#include<iostream>
#include<iomanip>
#include<algorithm>
using namespace std;
struct money{
	double kg,yu;
	double ku;
};
bool cmp(money a,money b){
	return a.ku>b.ku;
}
int main()
{
	int N,op=0;
	money T;
	cin>>N>>T.kg;
	money a[N],aji;
	aji.yu=0;
	for(int q=0;q<N;q++){
		cin>>a[q].kg>>a[q].yu;
		a[q].ku=a[q].yu/a[q].kg*1.0;
	}
	sort(a,a+N,cmp);
	while(T.kg-a[op].kg>=0){
		aji.yu+=a[op].yu;
		T.kg-=a[op].kg;
		op++;
	}
	aji.yu+=a[op].yu/(a[op].kg/T.kg);
	cout<<fixed<<setprecision(2)<<aji.yu;
	return 0;
}