#include <bits/stdc++.h>
using namespace std;
struct s{
	int m;
	int v;
	double b;
}a[10001];
bool cmp(s a,s d){
	return a.b>d.b;
}
int main(){
	int n,k;
	cin>>n>>k;
	for(int i=1;i<=n;i++){
		cin>>a[i].m>>a[i].v;
		a[i].b=a[i].v*1.0/a[i].m;
	}
	sort(a+1,a+1+n,cmp);
	double now=0,money=0;
	int i=1;
	while(now+a[i].m<=k){
		now+=a[i].m;
		money+=a[i].v;
		i++;
	}
	double x=k-now;
	money+=x*a[i].b;
	printf("%.2lf",money);
	return 0;
}