#include <bits/stdc++.h>
using namespace std;
long long n, m, k;
string s;
int MOD = 1e9 + 7;
const int INF = 1e9;
const long long INF64 = 2e18;
const double PI = 3.141592653589793238463;
long long ar[1000004], ar1[1000004], vis[1000004], pre[1000004], dp[3004][3004];
vector<long long> gr[1000004], path;
set<long long> myset;
pair<long long, long long> seg[1000004];
map<long long, long long> mymap;
long long c = 0;
string st1[1000004], st2[1000004];
vector<long long> arr[1000004];
int comp(pair<long long, long long> a, pair<long long, long long> b) {
  return a.second < b.second;
}
int gcd(int a, int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  cin >> n;
  double w, cargo;
  cin >> w;
  for (int i = 0; i < int(n); i++) cin >> ar[i];
  for (int i = 0; i < int(n); i++) cin >> ar1[i];
  if (ar[0] == 1 || ar1[0] == 1) return cout << -1, 0;
  cargo = w;
  w += w / (ar1[0] - 1);
  for (int i = n - 1; i > 0; i--) {
    if (ar[i] == 1 || ar1[i] == 1) return cout << -1, 0;
    w += w / (ar[i] - 1);
    w += w / (ar1[i] - 1);
  }
  w += w / (ar[0] - 1);
  return printf("%10.10f", w - cargo), 0;
}
