#include <bits/stdc++.h>
using namespace std;
const int N = 1000100;
double f[N];
double C(int n, int m) { return f[n] - f[m] - f[n - m]; }
void solve(int ncase) {
  int n, m;
  cin >> n >> m;
  f[1] = 0;
  for (int i = 2; i <= n * m; i++) {
    f[i] = f[i - 1] + log(i);
  }
  double ret = 0;
  for (int k = 1; k <= min(n, m); k++) {
    double s =
        C(m, k) + C(n * m - m, n - k) - C(n * m, n) + 2 * log(k) - 2 * log(n);
    ret += exp(s) * n;
  }
  cout << setprecision(16) << ret << endl;
}
int main() {
  int T = 1;
  int ncase = 0;
  while (T--) {
    solve(++ncase);
  }
}
