#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[1002], b[1002], n, m;
  while (cin >> n >> m) {
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++) cin >> b[i];
    double be = m;
    bool flag = 0;
    for (int i = n - 1; i >= 0; i--) {
      be = be * b[(i + 1) % n] / (b[(i + 1) % n] - 1);
      if (be > 1000000000) {
        flag = 1;
        break;
      }
      be = be * a[i] / (a[i] - 1);
    }
    if (flag)
      cout << -1 << endl;
    else
      cout << fixed << setprecision(10) << be - m << endl;
  }
  return 0;
}
