#include <bits/stdc++.h>
using namespace std;
int n, a[16], b[16];
int main() {
  double cnt = 0;
  ios::sync_with_stdio(false);
  cin >> n;
  for (register int i = 0; i < n; i++) cin >> a[i];
  for (register int i = 0; i < n; i++) cin >> b[i];
  for (register int i = 0; i < 1e6; ++i) {
    register bool f = false;
    for (register int j = 0; !f && j < n; ++j) f |= i % a[j] == b[j];
    cnt += f;
  }
  cout.setf(ios::fixed, ios::floatfield);
  return (cout << setprecision(7) << cnt / 1e6 << endl) && 0;
}
