// Move n disks from source to target through aux (Towers of Hanoi).

void Hanoi(int n, int source, int aux, int target) {
  if (n == 1) {
    // Move disk from `source` to `target`.
  } else {
    Hanoi(n - 1, source, target, aux);
    // Move disk from `source` to `target`.
    Hanoi(n - 1, aux, source, target);
  }
}