#include <bits/stdc++.h>   using namespace std;   int n, sum, m[17], r[17];   double ans;   int main() {     cin >> n;     for (int i = 1; i <= n; i++) cin >> m[i];     for (int i = 1; i <= n; i++) cin >> r[i];     for (int i = 1; i <= 999999; i++)       for (int j = 1; j <= n; j++)         if (i % m[j] == r[j]) {           sum++;           break;         }     ans = 1.0 * sum / 999999;     cout << ans;     return 0;   }   