#include <bits/stdc++.h>
using namespace std;
#define ppc __builtin_popcount
const int N = 25,Sz = 1 << 22;
typedef double db;
int n,a[N];
db f[Sz],b[N];
inline db Solve(int S) {
	db lim = 0;
	vector<int> id2;id2.reserve(n);
	for(int i = 0;i < n;i++) if((S >> i) & 1) {
		if(b[i] >= a[i]) lim = max<db>(lim,a[i]);
		else id2.push_back(i);
	}
		

	db sk = 0,sb = 0;
	for(int t = (int)id2.size() - 1;t >= 0;t--) {
		db L = !t ? 0 : a[id2[t - 1]],R = a[id2[t]];
		sk += 1.0 / (b[id2[t]] - a[id2[t]]);
		sb += (-a[id2[t]]) / (b[id2[t]] - a[id2[t]]);
		
		db x = (1 - sb) / sk;
		x = min(x,R);
		if(x >= L) lim = max(lim,x);
	}
	return lim;
}
int main() {
	// freopen("tmp.in","r",stdin);
	cin >> n;
	for(int i = 0;i < n;i++) cin >> a[i];
	sort(a,a + n);
	for(int S = 0;S < (1 << n);++S) {
		if(ppc(S) <= 1) continue;
		for(int i = 0;i < n;i++)
			if((S >> i) & 1) 
				b[i] = f[S - (1 << i)];
		f[S] = Solve(S);
	}
	printf("%.12lf\n",f[(1 << n) - 1]);
	// cerr << 1.0 * clock() / CLOCKS_PER_SEC << endl;
	return 0;
}