题解 | #Chocolate Buying#

#include <bits/stdc++.h>
using namespace std;
const int maxn = 100010;
struct Choc {
	long long P, C;
	bool operator<(const Choc& b) const {
		return P < b.P;
	}
} choc[maxn];
int main() {
	int N;
	long long B, res = 0;
	cin >> N >> B;
	for (int i = 1; i <= N; i++) {
		cin >> choc[i].P >> choc[i].C;
	}
	sort(choc + 1, choc + 1 + N);
	for (int i = 1; i <= N && B > 0; i++) {
		long long t = min(B / choc[i].P, choc[i].C);
		res += t;
		B -= t * choc[i].P;
	}
	cout << res;
}