#include<bits/stdc++.h>
using namespace std;
int n,t;
double sum;
struct gold{
	int h,j;
	double dj;
}a[101];
bool cmp(gold x,gold y){
	
		return x.dj>y.dj;
	
}
int main(){
	cin>>n>>t;
	for(int i=1;i<=n;i++){
		cin>>a[i].h>>a[i].j;
		a[i].j=a[i].j*1.0;
		a[i].dj=a[i].j/a[i].h;
	}
	sort(a+1,a+n+1,cmp);

	for(int i=1;i<=n;i++){
		if(a[i].h<=t){
			sum+=a[i].j;
			t-=a[i].h;
			
		}
		else{
			sum+=(t*a[i].dj);
			break;
		}
			
	
		
	}
	printf("%.2f",sum);
	return 0;
}