#include<bits/stdc++.h>
using namespace std;
int n,t;
struct coin{
	int m;
	int v;
	double x;
};
coin a[100];
bool cmp(coin i,coin j)
{
	return i.x>j.x; 
}
int main()
{
	double res=0;
	cin>>n>>t;
	for(int i=0;i<n;i++)
	{
		cin>>a[i].m>>a[i].v;
		a[i].x=1.0*a[i].v/a[i].m;
	}
	sort(a,a+100,cmp);
	for(int i=0;i<n;i++)
	{
		if(a[i].m>=t)
		{
			res+=a[i].x*t;
			printf("%.2f",res);
			return 0;
		}
		else
		{
			res+=a[i].v;
			t-=a[i].m;
		}
	}
	return 0;
}