#include<iostream>
#include<string>
#include<cmath>
#include<algorithm>
#include<cstdio>
using namespace std;
const int N=102;
int n,zhilian;
struct gold{
	double weight;
	double worth;
	double every;
}go[N];
bool compair(gold a,gold b){
	return a.every>b.every;
}
int main(){
	cin>>n>>zhilian;
	int i=0;
	int t=n;
	while(t--){
		int x1,x2;
		scanf("%d%d",&x1,&x2);
		go[i].weight=x1,go[i].worth=x2;
		go[i].every=(double)x2/x1;
		i++;	
	}
	sort(go,go+n,compair);
	double res=0;
	for(int j=0;j<n;j++){
		if(zhilian>go[j].weight) res+=go[j].worth,zhilian-=go[j].weight;
		else {
			res+=go[j].every*zhilian;
			break;
		}
	}
	printf("%.2lf",res);
	return 0;
	
}