#include <bits/stdc++.h>
using namespace std;
long double dp[1024][1024];
long double solve(int n, int m) {
  memset(dp, 0, sizeof(dp));
  int i, k;
  dp[1][1] = 1.0;
  for (i = 2; i <= n; i++) {
    for (k = 0; k <= n && k <= m && k <= n * m; k++) {
      dp[i][k] = 0.0;
      if (k > 0)
        dp[i][k] += dp[i - 1][k - 1] *
                    ((long double)(m - k + 1) / ((long double)n * m - i + 1));
      dp[i][k] += dp[i - 1][k] * ((long double)(m * n - i + 1 - (m - k)) /
                                  ((long double)n * m - i + 1));
    }
  }
  long double res = 0.0;
  for (i = 1; i <= n && i <= m; i++) {
    res += dp[n][i] * ((long double)i / (long double)n);
  }
  return res;
}
int main() {
  int n, m;
  cin >> n >> m;
  cout << solve(n, m) << endl;
  return 0;
}
