#include<iostream>
#include<iomanip>
#include<algorithm>
using namespace std;
struct treasure{
	int w,v;
	double dv;
}tr[111];
bool cmp(treasure a,treasure b){
	return a.dv>b.dv;
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n,t;
	cin>>n>>t;
	for(int i=1;i<=n;i++){
		cin>>tr[i].w>>tr[i].v;
		tr[i].dv=tr[i].v/tr[i].w;
	}
	sort(tr,tr+n+1,cmp);
	int i1=0;
	double ans;
	while(t>0){
		if(t>=tr[i1].w){
			t-=tr[i1].w;
			ans+=tr[i1].v;
		}else{
			ans+=t*tr[i1].dv;
			t=0;
		}
		i1++;
	}
    cout <<fixed<<setprecision(2)<<ans<< endl;
    return 0;
}