#include <bits/stdc++.h>
using namespace std;
const int INF = 1E9;
const double eps = 1e-9;
const double pi = acos(-1.0);
const int MAXN = 111;
int n, m;
double ans, cur, cnk, ch, ch2;
int main() {
  cin >> n >> m;
  ans = 0;
  for (int k = 0; k <= min(m - 1, n - 1); k++) {
    cur = 0;
    cnk = 1;
    for (int i = 1; i <= k; i++) cnk *= double(m - i) / (k - i + 1);
    for (int i = 1; i <= n - 1 - k; i++)
      cnk *= double((n - 1) * m - i + 1) / (n - 1 - k - i + 1);
    ch = 1;
    for (int i = 1; i <= n - 1; i++) ch *= double(n - 1 - i + 1) / (n * m - i);
    cur = cnk * ch * (k + 1) / n;
    ans += cur;
  }
  cout.precision(15);
  cout << ans;
  return 0;
}
