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OI-codes/Luogu/P5094/P5094.cpp

55 lines
1015 B
C++

#include <iostream>
#include <algorithm>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 5e4 + 5;
int n;
long long c1[N], c2[N], s, ans;
std::pair<int, int> p[N];
inline int lowbit(int x) {
return x & -x;
}
void add(long long* c, int x, int y) {
for (; x <= 5e4; x += lowbit(x)) c[x] += y;
}
long long sum(long long* c, int x) {
long long res = 0;
for (; x; x -= lowbit(x)) res += c[x];
return res;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> p[i].first >> p[i].second;
}
std::sort(p + 1, p + 1 + n);
for (int i = 1; i <= n; i++) {
int a = sum(c1, p[i].second),
b = sum(c2, p[i].second);
ans += ((a * p[i].second - b) + ((s - b) - (i - a - 1) * p[i].second)) * p[i].first;
add(c1, p[i].second, 1);
add(c2, p[i].second, p[i].second);
s += p[i].second;
}
cout << ans << endl;
return 0;
}