This documentation is automatically generated by online-judge-tools/verification-helper
#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/lesson/2/ITP1/1/ITP1_1_A"
// #define PROBLEM "https://atcoder.jp/contests/abc292/tasks/abc292_ex"
#define ERROR 1e-9
#include "../../Src/Template/IOSetting.hpp"
#include "../../Src/Algebra/Monoid/AdditionMonoid.hpp"
#include "../../Src/Algebra/Monoid/MaxMonoid.hpp"
#include "../../Src/Algebra/Monoid/PrefixProductMonoid.hpp"
#include "../../Src/DataStructure/SegmentTree/SegmentTree.hpp"
#include <algorithm>
#include <cassert>
#include <iostream>
#include <optional>
#include <vector>
using namespace zawa;
using D = std::optional<long long>;
using vM = MaxMonoid<long long>;
struct oM {
using Element = D;
static D identity() noexcept {
return 0LL;
}
static D operation(const D& l, const D& r) noexcept {
if (l and r) return l.value() + r.value();
else return (l ? l : (r ? r : 0LL));
}
};
using M = PrefixProductMonoid<oM, vM>;
int main() {
#ifdef ATCODER
SetFastIO();
SetPrecision(10);
int n, q;
long long b;
std::cin >> n >> b >> q;
std::vector<M::Element> a(n);
for (int i{} ; i < n ; i++) {
long long v; std::cin >> v;
a[i] = M::Element{D{v - b}, D{v - b}};
}
SegmentTree<M> seg(a);
for (int _{} ; _ < q ; _++) {
int c; std::cin >> c;
c--;
long long x; std::cin >> x;
x -= b;
seg.set(c, M::Element{D{x}, D{x}});
auto r{seg.maxRight(0, [](const M::Element& v) -> bool { return (!(bool)v.prefix() or v.prefix().value() < 0LL); })};
r = std::min<int>(r + 1, n);
assert(seg.product(0, r).product().has_value());
long long sum{seg.product(0, r).product().value()};
long double ans{(long double)(sum + b * (long long)r) / (long double)r};
std::cout << ans << '\n';
}
#else
std::cout << "Hello World\n";
#endif
}
#line 1 "Test/AtCoder/abc292_h.test.cpp"
#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/lesson/2/ITP1/1/ITP1_1_A"
// #define PROBLEM "https://atcoder.jp/contests/abc292/tasks/abc292_ex"
#define ERROR 1e-9
#line 2 "Src/Template/IOSetting.hpp"
#line 2 "Src/Template/TypeAlias.hpp"
#include <cstdint>
#include <cstddef>
namespace zawa {
using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;
using i128 = __int128_t;
using u8 = std::uint8_t;
using u16 = std::uint16_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;
using usize = std::size_t;
} // namespace zawa
#line 4 "Src/Template/IOSetting.hpp"
#include <iostream>
#include <iomanip>
namespace zawa {
void SetFastIO() {
std::cin.tie(nullptr)->sync_with_stdio(false);
}
void SetPrecision(u32 dig) {
std::cout << std::fixed << std::setprecision(dig);
}
} // namespace zawa
#line 2 "Src/Algebra/Monoid/AdditionMonoid.hpp"
namespace zawa {
template <class T>
struct AdditionMonoid {
using Element = T;
static T identity() noexcept {
return T{};
}
static T operation(const T& a, const T& b) noexcept {
return a + b;
}
};
} // namespace zawa
#line 2 "Src/Algebra/Monoid/MaxMonoid.hpp"
#include <algorithm>
#include <limits>
#include <optional>
namespace zawa {
template <class T>
class MaxMonoid {
public:
using Element = std::optional<T>;
static constexpr Element identity() noexcept {
return std::nullopt;
}
static constexpr Element operation(const Element& l, const Element& r) noexcept {
if (l and r) {
return std::max(l, r);
}
else if (l) {
return l;
}
else if (r) {
return r;
}
else {
return std::nullopt;
}
}
};
} // namespace zawa
#line 2 "Src/Algebra/Monoid/PrefixProductMonoid.hpp"
#include <type_traits>
namespace zawa {
template <class Value>
class PrefixProductMonoidData {
Value product_{}, prefix_{};
public:
PrefixProductMonoidData() = default;
PrefixProductMonoidData(const Value& product, const Value& prefix)
: product_{product}, prefix_{prefix} {}
inline const Value& product() const noexcept {
return product_;
}
inline const Value& prefix() const noexcept {
return prefix_;
}
};
template <class O, class F>
class PrefixProductMonoid {
static_assert(std::is_same_v<typename O::Element, typename F::Element>);
public:
using Element = PrefixProductMonoidData<typename O::Element>;
static Element identity() noexcept {
return PrefixProductMonoidData{O::identity(), F::identity()};
}
static Element operation(const Element& l, const Element& r) noexcept {
return PrefixProductMonoidData{
O::operation(l.product(), r.product()),
F::operation(l.prefix(), O::operation(l.product(), r.prefix()))
};
}
};
} // namespace zawa
#line 2 "Src/DataStructure/SegmentTree/SegmentTree.hpp"
#line 2 "Src/Algebra/Monoid/MonoidConcept.hpp"
#line 2 "Src/Algebra/Semigroup/SemigroupConcept.hpp"
#include <concepts>
namespace zawa {
namespace concepts {
template <class T>
concept Semigroup = requires {
typename T::Element;
{ T::operation(std::declval<typename T::Element>(), std::declval<typename T::Element>()) } -> std::same_as<typename T::Element>;
};
} // namespace concepts
} // namespace zawa
#line 4 "Src/Algebra/Monoid/MonoidConcept.hpp"
#line 6 "Src/Algebra/Monoid/MonoidConcept.hpp"
namespace zawa {
namespace concepts {
template <class T>
concept Identitiable = requires {
typename T::Element;
{ T::identity() } -> std::same_as<typename T::Element>;
};
template <class T>
concept Monoid = Semigroup<T> and Identitiable<T>;
} // namespace
} // namespace zawa
#line 5 "Src/DataStructure/SegmentTree/SegmentTree.hpp"
#include <vector>
#include <cassert>
#include <functional>
#line 10 "Src/DataStructure/SegmentTree/SegmentTree.hpp"
#include <ostream>
namespace zawa {
template <concepts::Monoid Monoid>
class SegmentTree {
public:
using VM = Monoid;
using V = typename VM::Element;
using OM = Monoid;
using O = typename OM::Element;
SegmentTree() = default;
explicit SegmentTree(usize n) : m_n{ n }, m_dat(n << 1, VM::identity()) {}
explicit SegmentTree(const std::vector<V>& dat) : m_n{ dat.size() }, m_dat(dat.size() << 1, VM::identity()) {
for (usize i{} ; i < m_n ; i++) {
m_dat[i + m_n] = dat[i];
}
for (usize i{m_n} ; i-- ; i) {
m_dat[i] = VM::operation(m_dat[left(i)], m_dat[right(i)]);
}
}
[[nodiscard]] inline usize size() const noexcept {
return m_n;
}
[[nodiscard]] V get(usize i) const {
assert(i < size());
return m_dat[i + m_n];
}
[[nodiscard]] V operator[](usize i) const {
assert(i < size());
return m_dat[i + m_n];
}
void operation(usize i, const O& value) {
assert(i < size());
i += size();
m_dat[i] = OM::operation(m_dat[i], value);
while (i = parent(i), i) {
m_dat[i] = VM::operation(m_dat[left(i)], m_dat[right(i)]);
}
}
void assign(usize i, const V& value) {
assert(i < size());
i += size();
m_dat[i] = value;
while (i = parent(i), i) {
m_dat[i] = VM::operation(m_dat[left(i)], m_dat[right(i)]);
}
}
[[nodiscard]] V product(u32 l, u32 r) const {
assert(l <= r and r <= size());
V L{ VM::identity() }, R{ VM::identity() };
for (l += size(), r += size() ; l < r ; l = parent(l), r = parent(r)) {
if (l & 1) {
L = VM::operation(L, m_dat[l++]);
}
if (r & 1) {
R = VM::operation(m_dat[--r], R);
}
}
return VM::operation(L, R);
}
template <class Function>
[[nodiscard]] usize maxRight(usize l, const Function& f) {
assert(l < size());
static_assert(std::is_convertible_v<decltype(f), std::function<bool(V)>>, "maxRight's argument f must be function bool(T)");
assert(f(VM::identity()));
usize res{l}, width{1};
V prod{ VM::identity() };
// 現在の見ている頂点の幅をwidthで持つ
// 境界がある頂点を含む部分木の根を探す
// (折り返す時は必要以上の幅を持つ根になるが、widthを持っているのでオーバーしない)
for (l += size() ; res + width <= size() ; l = parent(l), width <<= 1) if (l & 1) {
if (not f(VM::operation(prod, m_dat[l]))) break;
res += width;
prod = VM::operation(prod, m_dat[l++]);
}
// 根から下って、境界を発見する
while (l = left(l), width >>= 1) {
if (res + width <= size() and f(VM::operation(prod, m_dat[l]))) {
res += width;
prod = VM::operation(prod, m_dat[l++]);
}
}
return res;
}
template <class Function>
[[nodiscard]] usize minLeft(usize r, const Function& f) const {
assert(r <= size());
static_assert(std::is_convertible_v<decltype(f), std::function<bool(V)>>, "minLeft's argument f must be function bool(T)");
assert(f(VM::identity()));
usize res{r}, width{1};
V prod{ VM::identity() };
for (r += size() ; res >= width ; r = parent(r), width <<= 1) if (r & 1) {
if (not f(VM::operation(m_dat[r - 1], prod))) break;
res -= width;
prod = VM::operation(prod, m_dat[--r]);
}
while (r = left(r), width >>= 1) {
if (res >= width and f(VM::operation(m_dat[r - 1], prod))) {
res -= width;
prod = VM::operation(m_dat[--r], prod);
}
}
return res;
}
friend std::ostream& operator<<(std::ostream& os, const SegmentTree& st) {
for (usize i{1} ; i < 2 * st.size() ; i++) {
os << st.m_dat[i] << (i + 1 == 2 * st.size() ? "" : " ");
}
return os;
}
private:
constexpr u32 left(u32 v) const {
return v << 1;
}
constexpr u32 right(u32 v) const {
return v << 1 | 1;
}
constexpr u32 parent(u32 v) const {
return v >> 1;
}
usize m_n;
std::vector<V> m_dat;
};
} // namespace zawa
#line 10 "Test/AtCoder/abc292_h.test.cpp"
#line 16 "Test/AtCoder/abc292_h.test.cpp"
using namespace zawa;
using D = std::optional<long long>;
using vM = MaxMonoid<long long>;
struct oM {
using Element = D;
static D identity() noexcept {
return 0LL;
}
static D operation(const D& l, const D& r) noexcept {
if (l and r) return l.value() + r.value();
else return (l ? l : (r ? r : 0LL));
}
};
using M = PrefixProductMonoid<oM, vM>;
int main() {
#ifdef ATCODER
SetFastIO();
SetPrecision(10);
int n, q;
long long b;
std::cin >> n >> b >> q;
std::vector<M::Element> a(n);
for (int i{} ; i < n ; i++) {
long long v; std::cin >> v;
a[i] = M::Element{D{v - b}, D{v - b}};
}
SegmentTree<M> seg(a);
for (int _{} ; _ < q ; _++) {
int c; std::cin >> c;
c--;
long long x; std::cin >> x;
x -= b;
seg.set(c, M::Element{D{x}, D{x}});
auto r{seg.maxRight(0, [](const M::Element& v) -> bool { return (!(bool)v.prefix() or v.prefix().value() < 0LL); })};
r = std::min<int>(r + 1, n);
assert(seg.product(0, r).product().has_value());
long long sum{seg.product(0, r).product().value()};
long double ans{(long double)(sum + b * (long long)r) / (long double)r};
std::cout << ans << '\n';
}
#else
std::cout << "Hello World\n";
#endif
}