#include<bits/stdc++.h>
using namespace std;
struct jb{
	float xjb;
	int zl;
	int jz;
}a[100001];
int n,bbrl;
float sum=0;
int main(){
	cin>>n>>bbrl;
	for(int i=0;i<n;i++){
		cin>>a[i].zl>>a[i].jz;
		a[i].xjb=a[i].jz/a[i].zl;
	}
	for(int i=0;i<n;i++){
		for(int j=0;j<i;j++){
			if(a[i].xjb>a[j].xjb){
				swap(a[i],a[j]);
			}
		}
	}
	for(int i=0;i<n;i++){
		if(bbrl>=a[i].zl){
			sum+=a[i].jz;
			bbrl-=a[i].zl;
		}else{
			sum+=a[i].xjb*bbrl;
			break;	
		}
	}
	printf("%0.2f",sum);
	return 0;
}