#include<bits/stdc++.h>

using namespace std;

typedef long long LL;
typedef pair<int, int> PII;

#define ios ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
#define f first
#define s second
#define endl "\n"

const int N=2e5+10;
const double eps =1e-9;

LL n,k;
int a[N];

bool check(double x)
{
    LL res=0;

    for(int i=1;i<=n;i++)
    {
        res+=(LL)floor(1.0*a[i]/x);
    }

    return res>=k;
}

int main()
{
    ios;
    cin>>n;
    for(int i=1;i<=n;i++)cin>>a[i];

    cin>>k;

    double l=eps,r=1e9;

    while(r>l+1e-9)
    {
        double mid=(l+r)/2;
        if(check(mid))l=mid;
        else r=mid;
    }

    cout<<fixed<<setprecision(15)<<l<<endl;


    return 0;
}

//rrrbb
//6.666666666666667
//6.6666666666662877