#include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     vector<double> a(n), b(n);     for (int i = 0; i < n; i++) {       cin >> a[i];       if (a[i] <= 1) {         printf( -1 n );         exit(0);       }     }     for (int i = 0; i < n; i++) {       cin >> b[i];       if (b[i] <= 1) {         printf( -1 n );         exit(0);       }     }     double s = m;     s += s / (b[0] - 1);     for (int i = n - 1; i >= 1; i--) {       s += s / (a[i] - 1);       s += s / (b[i] - 1);     }     s += s / (a[0] - 1);     printf( %.10f n , s - m);     return 0;   }   