#include<bits/stdc++.h>
using namespace std;

struct gold{
	float m,v,x;
	}p[101];
int n;
float t,haven=0.00;
inline bool cmp(gold a,gold b){
    return a.x >b.x; 
}	
int main(){
	cin>>n>>t;
	for(int i=1;i<n;i++){
		cin>>p[i].m>>p[i].v;
		p[i].x=p[i].v*1.00/p[i].m*1.00;
	}
	sort(p+1,p+n+1,cmp);
	for(int i=1;t!=0&&i<=n;i++){
			if(p[i].m>=t){
			haven+=t*p[i].x;
			t=0;
		}
		if(p[i].m<t){ 
			haven+=p[i].v;
			t-=p[i].m;
		}
	}
	printf("%.2f",haven);
	return 0;
}