#include<bits/stdc++.h>
using namespace std;
int n,m;
float ans;
struct jb{
	int pj;
	int pz;
	float xjb;
}ab[1005];
bool cmp(jb x,jb y)
{
	return x.xjb>=y.xjb;
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>ab[i].pz>>ab[i].pj;
		ab[i].xjb=ab[i].pj/ab[i].pz*1.0;
	}
	sort(ab+1,ab+1+n,cmp);
	for(int i=1;i<=n;i++)
	{                   
		if(ab[i].pz<m)
		{
			ans+=ab[i].pj;
			m-=ab[i].pz;
		}
		if(ab[i].pz>m)
		{
			ans+=m*ab[i].xjb*1.0;
			break;
		}
	}
	printf("%.2lf",ans);
	return 0;
}