#include <bits/stdc++.h>
using namespace std;
double F[1000009];
double C(int n, int m) { return F[n] - F[m] - F[n - m]; }
int main() {
  for (int i = 1; i < 1000009; i++) F[i] = F[i - 1] + log(i);
  int n, m;
  scanf("%d%d", &n, &m);
  double ans = 0;
  for (int i = 1; i <= n && i <= m; i++) {
    double cur = 0;
    cur += C(m, i);
    cur += C(m * (n - 1), n - i);
    cur -= C(m * n, n);
    cur += 2 * log(i);
    cur -= log(n);
    ans += exp(cur);
  }
  printf("%.10f\n", ans);
}
