#include <bits/stdc++.h>
using namespace std;
double d[1111][1111];
int main() {
  int n, m, i, j;
  double ans;
  scanf("%d%d", &n, &m);
  d[0][0] = 1;
  for (i = 0; i < n; i++) {
    for (j = 0; j <= min(m, i); j++) {
      d[i + 1][j] += d[i][j] * ((n - 1) * m - i + j) / (n * m - i);
      d[i + 1][j + 1] += d[i][j] * (m - j) / (n * m - i);
    }
  }
  ans = 0;
  for (i = 0; i <= min(n, m); i++) {
    ans += d[n][i] * i * i / n;
  }
  printf("%.15lf", ans);
  return 0;
}
