#include <bits/stdc++.h>
using namespace std;
long double C(int x, int y) {
  long double re = 1;
  for (int yi = 1; yi <= y; yi++) {
    re *= x - yi + 1;
    re /= yi;
  }
  return re;
}
int N, M;
long double Ans = 0;
int main() {
  scanf("%d %d", &N, &M);
  for (int i = 1, n = min(N, M); i <= n; i++)
    Ans += C(M, i) * C(M * N - M, N - i) * i * i;
  Ans /= N * C(M * N, N);
  printf("%.9lf\n", (double)Ans);
}
