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OI-codes/AtCoder/ABC258/D/D.cpp

30 lines
489 B
C++

#include <iostream>
#include <limits>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 2e5 + 5;
int n, x, a, b;
long long sum, ans = std::numeric_limits<long long>::max();
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> x;
for (int i = 1; i <= std::min(x, n); i++) {
cin >> a >> b;
sum += a + b;
ans = std::min(ans, sum + 1ll * (x - i) * b);
}
cout << ans << endl;
return 0;
}