#include <bits/stdc++.h>
using namespace std;
int main() {
  double weight = 0;
  long n, m;
  cin >> n >> m;
  long long a[n];
  long long b[n];
  bool flag = 0;
  for (long i = 0; i < n; i++) {
    cin >> a[i];
    if (a[i] == 1) {
      flag = 1;
    }
  }
  for (long i = 0; i < n; i++) {
    cin >> b[i];
    if (b[i] == 1) {
      flag = 1;
    }
  }
  if (flag == 1) {
    cout << -1 << endl;
    exit(0);
  }
  weight = m;
  weight += double(weight) / double(b[0] - 1);
  for (long i = n - 1; i > 0; i--) {
    weight += double(weight) / double(a[i] - 1);
    weight += double(weight) / double(b[i] - 1);
  }
  weight += double(weight) / double(a[0] - 1);
  cout << setprecision(30) << weight - m << endl;
}
