#include <bits/stdc++.h>
using namespace std;
int n, m;
double ans = 0;
double a[1000001] = {0};
double b[1000001] = {0};
double combine(int n, int m) {
  if (n < m)
    return -1e100;
  else
    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];
  }
  for (int k = 1; k <= n; k++) {
    ans += exp(2 * a[k] + a[n] + combine(m, k) + combine((n - 1) * m, n - k) -
               2 * a[n] - combine(n * m, n));
  }
  printf("%.9lf", ans);
  return 0;
}
