#include<bits/stdc++.h>
using namespace std;
bool cmp(double x,double y){
	return x>y;
}
int main(){
	int n,t;
	cin>>n>>t;
	double w[101],j[101];
	double p[101];
	for(int i=0;i<n;i++){
	cin>>w[i]>>j[i];
	p[i] =j[i]/w[i];
	}
	sort(p,p+n,cmp);
	double sum=0;
	for(int i=0;i<n;i++){
		if(t>=w[i]){
		t-=w[i];
		sum+=j[i];}
		else {
			sum+=t*p[i];
			break;
		}
	}
	printf("%.2lf",sum);
	return 0;
}