#include <bits/stdc++.h>
using namespace std;
const int Direction[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
const int Nmax = 303000;
long double n, m;
long double ans = 0;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n >> m;
  long double r = n * m;
  for (int k = 1; k <= min(n, m); k++) {
    long double add = 1. * k * k / (long double)n;
    for (double i = n - k + 1; i <= n; i++)
      add = (add * (long double)(i)) / (long double)(i - n + k);
    for (double i = r - m - n + k + 1; i <= r - n; i++)
      add = (add * (long double)(i)) / (long double)(i + n - k);
    for (double i = 1; i <= k; i++)
      add = (add) * (m - k + i) / (long double)(r - k + i);
    ans += add;
  }
  cout.precision(16);
  cout << fixed << ans << endl;
  return 0;
}
