#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 2e5+10;
const int M = 2e5+10;
const int INF = 0x3f3f3f3f;

int a[N];

int main(void)
{
//	ios::sync_with_stdio(false);
//	cin.tie(false); cout.tie(false);
	int n;
	cin >> n;
	for(int i = 0; i < n; ++i) cin >> a[i];
	sort(a, a+n);
	ll up = 1, down = a[0];
	for(int i = 1; i < n; ++i) {
		up = down+up*a[i];
		down *= a[i];
		ll g = __gcd(up, down);
		up /= g; down /= g;
	}
	printf("%.5f\n", (double)down/up);
	return 0;
 } 