#include <bits/stdc++.h>   using namespace std;   int main() {     std::ios::sync_with_stdio(false);     int n;     double m, mm;     cin >> n >> mm;     m = mm;     double *a = new double[n];     double *b = new double[n];     for (int i = 0; i < n; ++i) {       cin >> a[i];       if (a[i] == 1) {         cout << -1;         return 0;       }     }     for (int i = 0; i < n; ++i) {       cin >> b[i];       if (b[i] == 1) {         cout << -1;         return 0;       }     }     double x = m / (b[0] - 1);     m += x;     for (int i = n - 1; i > 0; --i) {       x = m / (a[i] - 1);       m += x;       x = m / (b[i] - 1);       m += x;     }     x = m / (a[0] - 1);     m += x;     cout << fixed << setprecision(10) << m - mm;     return 0;   }   