#include<cstdio>
#define rep(i,a) for(int i=0;i<(a);++i)

typedef long long ll;

const int MAX_N = 200000;

ll N;
ll L[MAX_N];
ll K;

bool C( double x )
{
	ll cnt = 0;

	rep( i, N )
		cnt += int(L[i]/x);

	return cnt >= K;
}

int main()
{
	scanf( "%lld", &N );
	rep( i, N )
		scanf( "%lld", L+i );
	scanf( "%lld", &K );

	double lb = 0, ub = 1e9;
	rep( i, 1000 )
	{
		double mid = (lb+ub)/2;

		if( C( mid ) )
			lb = mid;
		else
			ub = mid;
	}

	printf( "%.9f\n", lb );

	return 0;
}