#include <bits/stdc++.h>
using namespace std;
int n, m;
double p[1010];
int main() {
  scanf("%d%d", &n, &m);
  if (n == 1) {
    printf("1.00000000000\n");
    return 0;
  }
  if (m == 1) {
    printf("%.12lf\n", 1.0 / n);
    return 0;
  }
  p[0] = 1.0;
  for (int i = 1; i <= m; i++) {
    p[0] = p[0] * (n * m - m - n + i) / (n * m - m + i);
  }
  double ans = 0.0;
  for (int i = 1; i <= m; i++) {
    p[i] = p[i - 1] * (m - i + 1) * (n - i + 1) / i / (n * m - m - n + i);
    ans += p[i] * i * i / n;
  }
  printf("%.12lf\n", ans);
}
