#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int* m = new int[n];
  int* r = new int[n];
  for (int i = 0; i < n; i++) {
    cin >> m[i];
  }
  for (int i = 0; i < n; i++) {
    cin >> r[i];
  }
  double total = 0;
  for (int i = 0; i < 1000000; i++) {
    for (int j = 0; j < n; j++) {
      if (i % m[j] == r[j]) {
        total++;
        break;
      }
    }
  }
  double percentage = total / 1000000;
  cout << fixed << setprecision(6) << percentage << endl;
}
