#include <bits/stdc++.h>

typedef long long ll;
typedef unsigned long long ull;

#define FOR(i,a,b) for(int (i)=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define RANGE(vec) (vec).begin(),(vec).end()

using namespace std;


class CuttingStick1 {
public:
    void solve(void) {
            int N;
            cin>>N;
            vector<double> L(N);
            REP(i,N)
                cin>>L[i];
            ll K;
            cin>>K;
            // ある長さ D の棒を K 本つくれるならそれ以下の長さの棒も作れる
            // よって二分探索すればよい

            double high = 1E+9;
            double low  = 0;

            REP(i, 100)
            {
                if (abs(high-low) < 1e-9)
                    break;
                double mid = (high+low)*0.5;
                auto tmp = L;

                ll     k = 0;
                size_t j = 0;
                while (j < tmp.size())
                {
                    if (k == K)
                        break;
                    if (tmp[j] < mid)
                        ++j;
                    else if (tmp[j] >= mid)
                    {
                        tmp[j] -= mid;
                        ++k;
                    }
                }
                if (k == K)
                    low = mid;
                else
                    high = mid;
            }
            cout<<setprecision(20)<<low<<endl;
    }
};

#if 1
int main(int argc, char *argv[])
{
        ios::sync_with_stdio(false);
        auto obj = new CuttingStick1();
        obj->solve();
        delete obj;
        return 0;
}
#endif