#include<bits/stdc++.h>
using namespace std;
struct coin{
	int m;
	int v;
} ;coin a[9999];
bool cmp(coin c,coin b){
	return (c.v*1.0/c.m)>b.v*1.0/b.m;
}
int main(){
	int n,bag,price;
	cin>>n>>bag;
	int i,j;
	for(i=1;i<=n;i++)
	cin>>a[i].m>>a[i].v;
	sort(a+1,a+n+1,cmp);
	for(i=1;i<=n;i++){
		if(a[i].m<bag){
			bag-=a[i].m;
			price+=a[i].v;
		}
		else{
			price=price+bag*a[i].v*1.0/a[i].m;
			break;
		}
	}
	printf("%.2f\n",float(price));
	return 0;
} 

请各位大佬康康，本蒟蒻将无限感谢！！