#include <bits/stdc++.h>
int n, m;
double ans;
int main() {
  while (scanf("%d %d", &n, &m) == 2) {
    ans = 0.0;
    for (int i = 1; i <= std::min(m, n); ++i) {
      double tmp = 1.0;
      for (int j = 0; j < i; ++j) {
        tmp = tmp * (m - j) / (j + 1);
      }
      for (int j = 0; j < n - i; ++j) {
        tmp = tmp * ((n - 1) * m - j) / (j + 1);
      }
      for (int j = 0; j < n; ++j) {
        tmp = tmp * (j + 1) / (n * m - j);
      }
      ans += tmp * i * i / n;
    }
    printf("%.18lf\n", ans);
  }
  return 0;
}
