#include<bits/stdc++.h>
using namespace std;
struct coin{
	int m,v;
}a[999];
bool cmp(coin x,coin y){
	return x.v*y.m>y.v*x.m;
} 
int main(){
	int n,t,i;
	float ans=0;
	cin>>n>>t;
	for(int i=0;i<n;i++){
		cin>>a[i].m>>a[i].v;
	}
	sort(a,a+n,cmp);
	for(int i=0;i<n;i++){
		if(a[i].m>t)
		break;
		t-=a[i].m;
		ans+=a[i].v;}
	if(i<n){
		ans+=1.0*t/a[i].m*a[i].v;
	}
	printf("%.2f",ans);
	return 0;
 }