#include <bits/stdc++.h>
using namespace std;
int main() {
  int nn, mm;
  scanf("%d%d", &nn, &mm);
  double ans = 0, n = nn, m = mm;
  for (int i = 1; i <= min(nn, mm); i++) {
    double tmp = nn;
    for (int j = 1; j <= i; j++)
      tmp *= (m + 1 - j) / (n * m + 1 - j), tmp *= (n + 1 - j) / j;
    for (int j = i + 1; j <= nn; j++)
      tmp *= (n * m - m + 1 - (j - i)) / (n * m + 1 - j);
    tmp *= (i / n) * (i / n);
    ans += tmp;
  }
  printf("%.16f", ans);
  return 0;
}
