80分第一个点始终RE，求救大佬

#include<bits/stdc++.h>
using namespace std;
	struct coin{
		int m,v;
		double bi;
	}a[1005]; 
	bool cmp(coin x,coin y){
		return x.bi>y.bi;
	}
int main(){
	int n,t,now=0,sign=1;
	double sum=0;
	cin>>n>>t;
	for(int i=1;i<=n;i++){
		cin>>a[i].m>>a[i].v;
		a[i].bi = a[i].v*1.0 / a[i].m;
	}
	sort(a+1,a+1+n,cmp);
	while(now+a[sign].m<t){
		now+=a[sign].m;
		sum+=a[sign].v;
		sign++;
	}
	sum+=a[sign].bi*(t-now);
	printf("%.2f",sum);
	
	return 0;
}