#include <bits/stdc++.h>
int n, m;
double lg[1000001];
double logC(int a, int b) { return lg[a] - lg[b] - lg[a - b]; }
int main() {
  lg[0] = 0;
  for (int i = 1; i <= 1000000; i++) lg[i] = lg[i - 1] + log(i);
  while (scanf("%d%d", &n, &m) == 2) {
    double ans = 0;
    for (int i = 1; i <= n && i <= m; i++)
      ans += (double)(i * i) *
             exp(logC(m, i) + logC(m * n - m, n - i) - logC(n * m, n)) / n;
    printf("%.17lf\n", ans);
  }
}
