#include <bits/stdc++.h>
using namespace std;
const int inv = 1000000000;
const int minv = -inv;
const int max_n = 1010;
int n, m;
double f[max_n];
int main() {
  scanf("%d", &n);
  scanf("%d", &m);
  if (n == 1) {
    printf("1.00000000\n");
    return 0;
  }
  if (m == 1) {
    printf("%.6f\n", 1.0 / (double)n);
    return 0;
  }
  f[0] = 1.0;
  int r = (n - 1) * m;
  int t = n * m;
  for (int i = 0; i < n; i++) f[0] *= (double)(r - i) / (double)(t - i);
  double res = 0.0;
  for (int s = 1; s <= min(n, m); s++) {
    f[s] = f[s - 1] * (double)((n - s + 1) * (m - s + 1)) /
           (double)(s * (r - n + s));
    res += f[s] * (double)(s * s) / (double)n;
  }
  printf("%.6f\n", res);
  return 0;
}
