#include<bits/stdc++.h>
using namespace std;
struct node {
	int m,v;
	double p;
};
node a[110];
int n,t;
bool cmp (node x,node y) {
	return x.p>y.p;
}
int main (){
    cin>>n>>t;
    for (int i=1;i<=n;i++) {
    	cin>>a[i].m>>a[i].v;
    	a[i].p=a[i].v/a[i].m;
	}
	sort(a+1,a+n+1,cmp);
	double ans=0.0;
	for (int i=1;i<=n;i++){
		if (a[i].m<=t) {
			t-=a[i].m;
			ans+=a[i].v;
		} 
		else {
			ans+=a[i].p*t;
			break;
		}
	}
	printf ("%.2f",ans);
return 0;
}