#include <bits/stdc++.h>
using namespace std;
int n, m;
double C(double a, double b) {
  double t = 1;
  for (int i = 1; i <= b; i++) {
    t *= (a - b + i);
    t /= i;
  }
  return t;
}
int main() {
  cin >> n >> m;
  double ans = 0.0;
  for (int i = 1; i <= n; i++) {
    double pi = C(m, i) / C(n * m, n) * C(n * m - m, n - i);
    ans += pi * ((i * 1.0 / n) * (i * 1.0 / n));
  }
  ans *= n;
  printf("%.8f\n", ans);
}
