#include <bits/stdc++.h>
using namespace std;
double P[1001][1001];
int main() {
  int n, m;
  cin >> n >> m;
  P[0][0] = 1;
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j <= m; ++j) {
      double prob = double(m - j) / (n * m - i);
      P[i + 1][j + 1] += prob * P[i][j];
      P[i + 1][j] += (1 - prob) * P[i][j];
    }
  }
  double res = 0;
  for (int i = 1; i <= m; ++i) {
    res += i * i * P[n][i];
  }
  cout.setf(ios::floatfield, ios::fixed);
  cout.precision(8);
  cout << res / n << endl;
  return 0;
}
