#include <bits/stdc++.h>
using namespace std;
int n, m;
long double a[1000010], b[1000010];
long double C(int n, int m) {
  if (n < m) return -1e100;
  return b[n] - b[m] - b[n - m];
}
int main() {
  cin >> n >> m;
  for (int i = 1; i <= n * m; ++i) {
    a[i] = log(i);
    b[i] = b[i - 1] + a[i];
  }
  long double ans = 0;
  for (int k = 1; k <= n; ++k) {
    ans = ans +
          exp(2 * a[k] + C(m, k) + C((n - 1) * m, n - k) - a[n] - C(n * m, n));
  }
  printf("%.9f\n", (double)ans);
  return 0;
}
