#include <bits/stdc++.h>
using namespace std;
long double f[1011][1011];
int m, n;
void init() {
  memset(f, 0, sizeof f);
  f[1][1] = 1;
  for (int i = (1), _b = (n - 1); i <= _b; i++) {
    for (int x = (0), _b = (min(i, m)); x <= _b; x++)
      if (f[i][x] > 1e-50) {
        f[i + 1][x] += f[i][x] * ((m * n - m) - (i - x)) / (double)(m * n - i);
        f[i + 1][x + 1] += f[i][x] * (m - x) / (double)(m * n - i);
      }
  }
}
int main() {
  ios ::sync_with_stdio(false);
  cout << (fixed) << setprecision(8);
  while (cin >> n >> m) {
    init();
    double res = 0.0;
    for (int k = (1), _b = (min(m, n)); k <= _b; k++) {
      res += f[n][k] * k / (double)n;
    }
    cout << res << endl;
  }
  return 0;
}
