#include <bits/stdc++.h>
using namespace std;
int n, m;
long double C(int n, int m) {
  if (m > n) return 0;
  if (m > n / 2) m = n - m;
  long double ret = 1;
  for (int i = 0; i <= m - 1; i++) ret = ret * (n - i) / (m - i);
  return ret;
}
int main() {
  scanf("%d%d", &n, &m);
  long double ans = 0;
  for (int i = 1; i <= n; i++) {
    ans += ((double)i) * ((double)i / n) * C(m, i) *
           (C(n * m - m, n - i) / C(n * m, n));
  }
  printf("%.8f\n", (double)ans);
  return 0;
}
