#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;   }   