#include <bits/stdc++.h>
using namespace std;
double calcC(int N, int M) {
  if (M > N) return 0;
  M = min(N - M, M);
  double res = 1;
  for (int i = 1; i <= M; ++i) res *= N - M + i, res /= i;
  return res;
}
int main() {
  int N, M;
  while (cin >> N >> M) {
    double result = 0;
    for (int k = 1; k <= N; ++k) {
      double tmp = 1;
      tmp = calcC(M, k) * calcC(N * M - M, N - k) * k * k;
      tmp /= calcC(N * M, N) * N * N;
      result += tmp;
    }
    result *= N;
    cout << setprecision(10) << result << endl;
  }
}
