#include <bits/stdc++.h>
using namespace std;
double F[1000010];
double logC(int n, int k) { return F[n] - F[k] - F[n - k]; }
int main() {
  F[0] = 0;
  for (int i = 1; i < 1000010; i++) F[i] = F[i - 1] + log(i);
  int n, m;
  cin >> n >> m;
  double S = 0;
  for (int k = 0; k <= min(n, m); k++) {
    double T = 0;
    T -= log(n);
    T += logC(m, k);
    T += logC(m * (n - 1), n - k);
    T -= logC(m * n, n);
    T += 2 * log(k);
    S += exp(T);
  }
  printf("%.9lf\n", S);
  return 0;
}
