#include <bits/stdc++.h>
using namespace std;
const int N = 1000 + 7;
const int inf = 0x3f3f3f3f;
const long long INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-8;
int n, m;
double p[N][N];
int main() {
  scanf("%d%d", &n, &m);
  p[0][0] = 1;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j <= i; j++) {
      p[i + 1][j + 1] += p[i][j] * (m - j) / (n * m - i);
      p[i + 1][j] += p[i][j] * (n * m - i - m + j) / (n * m - i);
    }
  }
  double ans = 0;
  for (int i = 1; i <= m; i++) {
    ans += p[n][i] * i / n * i / n;
  }
  printf("%.12f\n", ans * n);
  return 0;
}
