#include <bits/stdc++.h>
using namespace std;
struct A
{
	int c;
	int v;
	double p;
}a[105];
bool cmp(A s,A q)
{
	return s.p>q.p;
}
int main()
{
	int n,t;
	double sum;
	//cout<<setiosflags(ios::fixed)<<setprecision(2);
	cin>>n>>t;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i].c>>a[i].v;
		a[i].p=a[i].v/a[i].c;
	}
	sort(a+1,a+n+1,cmp);
	int i=1;
	while(t>0)
	{  
		if(t>=a[i].c)
		{
			sum+=a[i].v;
			t-=a[i].c;
		}
		else
		{
			sum+=a[i].p*t;
			t=0;
		}
		i++;
	}
	cout<<sum;
}