#include<iostream>
#include<algorithm>
using namespace std;
const int N=1e3;
int number,j;
double value,capacity,index;
struct money{
	double weight,valude,average;
}s[N];
bool cmp(money a,money b){
	return a.average>b.average;
}
int main(){
	scanf("%d%lf",&number,&capacity);
	for(int i=0;i<number;i++){
		scanf("%lf%lf",&s[i].weight,&s[i].valude);
		s[i].average=s[i].valude/s[i].weight;
	}
	sort(s,s+number,cmp);
	while(index+s[j].weight<=capacity){
			index+=s[j].weight;
			value+=s[j].valude;
			j++;
	}
	value+=(capacity-index)*s[j].average;
	printf("%.2lf",value);
	return 0;
} 

有一组数据RE了，找不出来错误