#include <bits/stdc++.h>
using namespace std;
long double c(int n, int p) {
  if (p > n - p) p = n - p;
  long double res = 1;
  for (int i = (1); i < (p + 1); ++i) {
    res *= (n - i + 1);
    res /= i;
  }
  return res;
}
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  long double res = 0;
  int k = ((n < m) ? (n) : (m)) + 1;
  for (int p = (1); p < (k); ++p) {
    long double val = c(m * n - m, n - p);
    val /= c(m * n, n);
    val *= c(m, p);
    val *= (p / (long double)n);
    val *= (p / (long double)n);
    res += val;
  }
  res *= n;
  printf("%.15lf\n", (double)res);
  return 0;
}
