#include <bits/stdc++.h>
using namespace std;
int a,t,c[105],d[105],j = 0,u = 0;double e[105],f[105],ans = 0;
int main(){
	cin>>a>>t;
	for(int i  =0;i<a;i++){
		cin>>c[i]>>d[i];
		e[i] = double(d[i])/double(c[i]);
		f[i] = e[i];
	}
	sort(e,e+a);a--;
	u = a;
	while(t>0){
		while(e[u] != f[j]){
			j++;
		}
		if(t>=c[j]){
			ans+=d[j];
			t-=c[j];
		}
		else{
			ans+=f[j]*t*1.0;
			break;
		}
		u--;
		j = 0;
	}
	printf("%.2lf",ans);
	return 0;
}