#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <map>
#include <stack>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#define FOR(i,x,n) for(long i=x;i<n;i++)
#define ll long long int
#define INF 0x3f3f3f3f
#define MOD 1000000007
#define MAX_N 50005

using namespace std;

struct node{int g,p;double unitPrice;};
node d[10005];

int cmp(node a,node b){
    return a.unitPrice>b.unitPrice;
}

int main()
{
    //freopen("input1.txt", "r", stdin);
    //freopen("data.out", "w", stdout);
    int N,W;
    scanf("%d %d",&N,&W);
    if(N==0&&W==0){
        printf("0");
    }
    int capacity=W;
    double value=http://www.mamicode.com/0;
    FOR(i,0,N){
        scanf("%d %d",&d[i].g,&d[i].p);
        d[i].unitPrice=d[i].p*1.0/d[i].g;
    }
    sort(d,d+N,cmp);
    FOR(i,0,N){
        if(capacity-d[i].g>0||capacity-d[i].g==0&&capacity==0){
            capacity-=d[i].g;
            value+=d[i].p;
        }else if(capacity-d[i].g==0&&capacity!=0){
            capacity-=d[i].g;
            value+=d[i].p;
            printf("%.1lf",value);
            return 0;
        }else if(capacity-d[i].g<0){
            value+=d[i].unitPrice*capacity;
            capacity=0;
            printf("%.1lf",value);
            return 0;
        }
    }
    printf("%.1lf",value);
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}
/*
3 0
0 1
0 2
1 1



*/