#include<bits/stdc++.h>
using namespace std;
double w[105],m[105];
int main(){
	int n;
	double v,ans=0,t;
	cin>>n>>t;
	for(int i=0;i<n;i++){
		cin>>m[i]>>v;
		w[i]=v/m[i];
	}
	for(int i=0;i<n-1;i++){
		for(int j=i;j<n-i-1;j++){
			if(w[j]>w[j+1]){
				swap(w[j],w[j+1]);
				swap(m[j],m[j+1]);
			}
		}
	}
	for(int i=n-1;i<=0;i--){
		if(t-m[i]<=0){
			ans+=(m[i]*t/m[i])*w[i];
			break;
		}
		ans+=m[i]*w[i];
		t-=m[i];
		//cout<<ans<<" "<<t<<" ";
	}
	printf("%.2lf",ans);
	return 0;
}