#include <bits/stdc++.h>
using namespace std;
template <class T>
inline T sqr(T x) {
  return x * x;
}
const double PI = acos(-1.0);
using namespace std;
double dp[1005][1005];
int main(void) {
  int n, m;
  scanf("%d %d", &n, &m);
  if (n == 1) {
    puts("1.0000000");
    return 0;
  }
  dp[0][0] = 1;
  for (int i = 1; i <= n - 1; i++) {
    dp[i][0] = dp[i - 1][0] * (1 - (m - 1.0) / (n * m - i));
    for (int j = 1; j <= i && j <= m; j++) {
      dp[i][j] = dp[i - 1][j - 1] * (m - j + 0.0) / (n * m - i) +
                 dp[i - 1][j] * (1 - (m - j - 1.0) / (n * m - i));
    }
  }
  double ans = 0;
  for (int i = 0; i <= n - 1; i++) {
    ans += dp[n - 1][i] * (i + 1.0) / n;
  }
  printf("%.10lf\n", ans);
  return 0;
}
