#include <bits/stdc++.h>
using namespace std;
int n, m;
long double c(int n, int m) {
  if (n - m < m) m = n - m;
  if (m == 0) return 1.0;
  if (m < 0) return 0.0;
  long double res = 1.0;
  for (int i = 1; i <= m; ++i) res = (res * (n - m + i)) / i;
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> m;
  long double res = 0;
  for (int i = 1; i <= m; ++i) res += c(m, i) * c(n * m - m, n - i) * i * i;
  res /= n;
  res /= c(n * m, n);
  cout << fixed << setprecision(15) << res;
  return 0;
}
