#include <bits/stdc++.h>
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("O3")
using namespace std;
const double eps = 1e-9;
const double pi = acos(-1.0);
const int inf = 2e5 + 10;
int mod = 1e9 + 7;
const int MAXN = 1e5 + 7;
long double C(int n, int k) {
  long double res = 1.;
  if (2 * k > n) k = n - k;
  for (int i = 1; i <= k; ++i) {
    res *= n - k + i;
    res /= i;
  }
  return res;
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  long double res = 0;
  for (int k = 1; k <= min(n, m); ++k) {
    res += C(m, k) * C(m * (n - 1), n - k) * k * k;
  }
  res /= n;
  res /= C(n * m, n);
  cout << res;
  return 0;
}
