#include <bits/stdc++.h>
using namespace std;
double lf[1000514];
double inf = 10e9;
double lc(int n, int m) { return lf[n] - lf[m] - lf[n - m]; }
int main() {
  int n, m;
  scanf("%d %d", &n, &m);
  lf[0] = 0;
  for (int i = 1; i <= 1000000; i++) {
    lf[i] = lf[i - 1] + log((double)i);
  }
  double ans = 0;
  for (int i = 0; i <= n; i++) {
    if (i <= m && n - i <= n * m - m) {
      ans += (double)i * (double)((double)i / n) *
             exp(lc(m, i) + lc(n * m - m, n - i) - lc(n * m, n));
    }
  }
  printf("%.10f\n", ans);
  return 0;
}
