#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;

long long sticks[200005];
long long countCuttedSticks(double cutLength) {
    long long count = 0;
    for (int stick: sticks) {
        count +=  stick / cutLength;
    }

    return count;
}

int main(void){
    // Your code here!
    int N;
    cin >> N;
    for (int i=0; i < N; i++) {
        cin>>sticks[i];
    }
    long long K;
    cin>>K;

    double high, low, ans;
    long long max = 0;
    for (int i=0; i < N; i++) {
        if (max < sticks[i])
            max = sticks[i];
    }
    high = (double)max;
    low = 0.0;

    if (countCuttedSticks(high) == K)
        cout << high << endl;
    else {
        for(int i = 0; i < 100; i++) {
            ans = (high + low) / 2.0;
            if (countCuttedSticks(ans) >= K)
                low = ans;
            else
                high = ans;
            // cout<<high<<","<<low<<endl;
        }
        cout<<fixed;
        cout << setprecision(11)<<ans<< endl;
    }
    return 0;
}