#include<bits/stdc++.h>

using namespace std;

int N,M;
struct abc{
	double v,c;
	double xj;
}a[1200];
double sum;
bool cmp(abc a,abc b)
{
	return a.xj>b.xj;
}

int main(){

cin>>N>>M;
for(int i=1;i<=N;i++)
{
	cin>>a[i].c>>a[i].v;
	a[i].xj=a[i].v/a[i].c;
}
sort(a+1,a+1+N,cmp);
for(int i=1;i<=N,M>0;i++)
{
//	cout<<a[i].v<<" "<<a[i].c<<"\n";
	if(a[i].c>M)
	{
		sum+=M*a[i].xj;
		break;
	}
	else
	{
		M-=a[i].c;sum+=a[i].v;
	}
}
printf("%.2lf",sum);
return 0;

}