#include<iostream>
#include <stdio.h>
#include<algorithm>
#include<math.h>
using namespace std;


struct node{
	
	double danjia;
	double milk;
	double danjia1;
	double zhon;
		
} a[1010];

bool cmp(node x, node y){
	return x.danjia1 > y.danjia1;
}

int main(){
	
	double ans;
	int t, m;
	cin >> m >> t;
	int t1 = t;
	for(int i = 0; i < m; i++){
		cin >> a[i].danjia >> a[i].milk;
		a[i].danjia1 = a[i].milk / a[i].danjia * 1.0;
	}
	sort(a, a + m, cmp);
	int o = 0;
	while(m){
		if(t >= a[o].danjia){
			ans += a[o].milk;
			t -= a[o].danjia;
		}
		if(t < a[o].danjia and t > 0){
			ans += a[o].danjia1;
			t--;
		}
		if(t <= 0){
			break;
		}
		o++;
		
	} 
	printf("%.2lf", ans);
	
	return 0;
}