#include<bits/stdc++.h>
using namespace std;
struct Gold
{
	int weight,value;
	double price;
}gold[110];
bool cmp(Gold a,Gold b)
{
	return a.price>=b.price;
}
int main()
{
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=n;++i)
	{
		cin>>gold[i].weight>>gold[i].value;
		gold[i].price=gold[i].value/(gold[i].weight*1.0);
	}
	sort(gold+1,gold+n+1,cmp);
	double jia=0;
	for(int i=1;i<=n;++i)
	{
		if(m>gold[i].weight)
		{
			m-=gold[i].weight;
			jia+=gold[i].value;
		}
		else
		{
			jia+=m*gold[i].price;
			break;
		}
	}
	printf("%.2llf",jia);
	return 0;
}