#include <bits/stdc++.h>
using namespace std;
double p[1005][1005];
int main() {
  int n, i, j, m, t;
  cin >> n >> m;
  t = n * m;
  p[1][1] = 1.0;
  for (i = 2; i <= n; i++)
    for (j = 0; j <= n; j++) {
      if (j > i)
        p[i][j] = 0.0;
      else if (j == 0)
        p[i][j] = 0.0;
      else {
        p[i][j] =
            p[i - 1][j] * ((t - i + 1 - m + j)) + p[i - 1][j - 1] * (m - j + 1);
        p[i][j] /= (t - i + 1);
      }
    }
  double prob = 0.0;
  for (i = 0; i <= n; i++) prob += p[n][i] * ((i) / (n * 1.0));
  printf("%.9lf\n", prob);
  return 0;
}
