#include <bits/stdc++.h>
using namespace std;
int row[] = {0, 1, 0, -1, -1, -1, 1, 1};
int col[] = {1, 0, -1, 0, 1, -1, -1, 1};
const long long N = 2e5 + 10;
const long long M = 1e18 + 7;
const long long H = 1e9 + 7;
const long long base = 131;
long long logx(long long a, long long bs) { return log(a) / log(bs); }
long long Max(long long a, long long b) {
  if (a > b) return a;
  return b;
}
long long Min(long long a, long long b) {
  if (a > b) return b;
  return a;
}
long long big_mul(long long a, long long b, long long m) {
  long long x = 0, y = a % m;
  while (b > 0) {
    if (b & 1) x = (x + y) % m;
    y = (2 * y) % m;
    b >>= 1;
  }
  return x % m;
}
long long big_mod(long long a, long long b, long long m) {
  long long x = 1, y = a % m;
  while (b > 0) {
    if (b & 1) x = (x * y) % m;
    y = (y * y) % m;
    b >>= 1;
  }
  return x % m;
}
long long Big_mod(long long a, long long b, long long m) {
  long long x = 1, y = a % m;
  while (b > 0) {
    if (b & 1) x = big_mul(x, y, m);
    y = big_mul(y, y, m);
    b >>= 1;
  }
  return x % m;
}
long long mod_inverse(long long a, long long m) { return big_mod(a, m - 2, m); }
long long GCD(long long a, long long b) {
  if (!a) return b;
  return GCD(b % a, a);
}
double l, r;
vector<double> vec1;
vector<double> vec2;
double fnct(double total, double value) { return total / value; }
bool possible(double x, double m) {
  double total = m + x;
  double need = fnct(total, vec1[0]);
  if (need > x) return false;
  x -= need;
  total = m + x;
  for (int i = 1; i < vec1.size(); i++) {
    need = fnct(total, vec2[i]);
    if (need > x) return false;
    x -= need;
    total = m + x;
    need = fnct(total, vec1[i]);
    if (need > x) return false;
    x -= need;
    total = m + x;
  }
  need = fnct(total, vec2[0]);
  if (need > x) return false;
  return true;
}
void bs(double m) {
  l = 0;
  r = (double)H;
  int cnt = 0;
  while (cnt++ <= 100) {
    double mid = (l + r) / 2.0;
    if (possible(mid, m) == true)
      r = mid;
    else
      l = mid;
  }
  if (l == H || r == H)
    cout << "-1" << endl;
  else
    printf("%0.10lf\n", l);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int n;
  cin >> n;
  double m;
  cin >> m;
  for (int i = 0; i < n; i++) {
    double a;
    cin >> a;
    vec1.push_back(a);
  }
  for (int i = 0; i < n; i++) {
    double a;
    cin >> a;
    vec2.push_back(a);
  }
  bs(m);
  return 0;
}
