#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  os << "[";
  for (__typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i) {
    if (i != v.begin()) os << ", ";
    os << *i;
  }
  os << "]";
  return os;
}
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  vector<double> P(m + 1, 0.0);
  P[0] = 1.0;
  for (int j = 0; j < (int)(n); ++j) {
    vector<double> Q(m + 1, 0.0);
    for (int i = (int)(0); i <= (int)(m); ++i) {
      double w = (double)(m - i) / (n * m - j);
      Q[i] += P[i] * (1 - w);
      if (i < m) Q[i + 1] += P[i] * w;
    }
    P.swap(Q);
  }
  double res = 0.0;
  for (int i = (int)(0); i <= (int)(m); ++i) res += ((i) * (i)) * P[i];
  res /= n;
  printf("%.9lf\n", res);
}
