#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
const int MAXN=1e4+7;
struct bag{
    int w,v;
    float val;
}b[MAXN];
int n,t;
bool cmp(bag a,bag b)
{
    return a.val>b.val;
}
int main()
{
    cin>>n>>t;
    for(int i=1;i<=n;i++)
    {
        cin>>b[i].w>>b[i].v;
        b[i].val=b[i].v/b[i].w;
    }
    sort(b+1,b+1+n,cmp);
    int i=1;
    float total=0.00;
    while(t>0)
    {
        if(i>n)
            break;
        if(t-b[i].w>0)
        {
            t=t-b[i].w;
            total+=b[i].v*1.0;
        }
        else
        {
            total+=t*b[i].val*1.0;
            t=0;
        }
        i++;
    }
    total*=1.0;
    printf("%.2f\n",total);
}