#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  double ans = 0.0;
  double mo = n, ch = 0.0;
  for (int i = 1; i <= n; i++) mo *= (double)(m * n - i + 1) / i;
  for (int i = min(n, m); i > 0; i--) {
    double tmp = i * i;
    for (int j = 1; j <= i; j++) tmp *= (double)(m - j + 1) / j;
    for (int j = n - i; j > 0; j--) tmp *= (double)((n - 1) * m - j + 1) / j;
    ch += tmp;
  }
  ans = ch / mo;
  printf("%.10f\n", ans);
  return 0;
}
