#include <bits/stdc++.h>
using namespace std;
const int Nmax = 1005;
double Dp[Nmax][Nmax];
int main() {
  int N, M;
  cin >> N >> M;
  Dp[0][0] = 1;
  for (int i = 1; i <= N; i++) {
    for (int j = 0; j <= M; j++) {
      double p1 = (double)(M - j) / ((double)(N * M - (i - 1)));
      double p2 = (double)(M - j + 1) / ((double)(N * M - (i - 1)));
      Dp[i][j] = Dp[i - 1][j] * (1 - p1) + (j > 0 ? Dp[i - 1][j - 1] * p2 : 0);
    }
  }
  double Sol = 0;
  for (int i = 1; i <= M; i++) Sol = Sol + Dp[N][i] * i * i / ((double)N);
  printf("%.14lf\n", Sol);
}
