// yukicoder: No.67 よくある棒を切る問題 (1)
// bal4u 2019.9.7

#include <stdio.h>
#include <stdlib.h>

typedef long long ll;

//// 高速入力
#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

ll inLL() {
	ll n = 0; int c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

#define EPS 1e-12
int N; ll K;
int L[200005];

inline static void chmax(ll *r, ll a) { if (*r < a) *r = a; }

ll cut(ll x) {
	int i; ll s = 0;
	for (i = 0; i < N; i++) s += L[i] / x;
	return s;
}

double fine(double l, double r) {
	int i, loop = 30; ll s; double m;
    while (loop--) {
      m = (l + r) / 2.0;
	  s = 0; for (i = 0; i < N; i++) s += (ll)((L[i]+EPS)/m + EPS);
	  if (s < K) r = m; else l = m;
    }
	return m;
}
	
int main()
{
	int i; ll l, r, m, ma;

	N = in(); 
	ma = 0; for (i = 0; i < N; i++) {
		L[i] = in(), chmax(&ma, L[i]);
	}
	K = inLL();
	l = 1; r = ma+1;
    while (l+1 < r) {
      m = (l + r) >> 1;
      if (cut(m) < K) r = m; else l = m;
    }
	if (cut(l) < K) r = l;
	printf("%.12lf\n", fine((double)r-1, (double)r));
	return 0;
}