直接上代码：

#include<bits/stdc++.h>
using namespace std;
struct coin{
	int m,v;
	double x;
}str[1005];
bool cmp(coin a,coin b){
	return a.x>b.x;
}
int main(){
	int n,t;
	double ans=0;
	scanf("%d%d",&n,&t);
	for(int i=1;i<=n;i++){
		scanf("%d%d",&str[i].m,&str[i].v);
		str[i].x=str[i].v*1.0/str[i].m;
	}
	sort(str+1,str+n+1,cmp);
	int i=1;
	while(t>0){
		if(str[i].m>t){
			ans=ans+t*str[i].x;
			break;
		}else{
			ans+=str[i].v;
			t-=str[i].m;
		}
		i++;
	}
	printf("%.2lf",ans);
	return 0;
}

到底哪的问题啊！！！！人都麻了