#include<iostream>
#include<algorithm>
#include<iomanip>
using namespace std; 
int n;
double cheng=0,ans=0;
struct need{
	double bi;
	int m;
	int v;
}a[1001];
bool cmp(need x,need y){
	return x.bi>y.bi;
}
int main(){
	cin>>n>>cheng;
	for(int i=1;i<=n;i++){
		cin>>a[i].m>>a[i].v;
		a[i].bi=a[i].v/a[i].m;
	}
	sort(a+1,a+n+1,cmp);
	for(int i=1;i<=n;i++){
		if(a[i].m<=cheng){
			cheng-=a[i].m;
			ans+=a[i].v;
		}
		else {
		ans+=a[i].bi*cheng;
		break;	
		}
	}
	cout<<fixed<<setprecision(2)<<ans;
	return 0;
}