（只有一个AC 其他全WA）

#include<bits/stdc++.h>
#define int long long
using namespace std;

struct node{
	int m, v;
	int mv;
}nd[1000];

bool cmd(node x, node y) {
	return x.mv<y.mv;
} 

signed main() {
	int n, t;
	cin >> n >> t;
	double ans = 0.00;
	for (int i = 0; i < n; i++) {
		cin >> nd[i].m >> nd[i].v;
		nd[i].mv = (1.0 * nd[i].v) / nd[i].m;
	}
	sort(nd, nd+n, cmd);
	for (int i = 0; i < n; i++) {
		if (t >= nd[i].m) {
			t -= nd[i].m;
			ans += nd[i].v;
		} else {
			ans += nd[i].mv*(nd[i].m-t);
			t = 0;
			break;
		}
	}
	printf("%.2f\n", ans);
	return 0;
}