int pos[8];
void queen(int n) {
 for (int i = 0; i < 8; i++) {
  pos[n] = i;
  bool attacked = false;
  for (int j = 0; j < n; j++)
   if (pos[n] == pos[j] || pos[n] + n == pos[j] + j || pos[n] - n == pos[j] - j) {
    attacked = true;
    break;
   }
  if (attacked)
   continue;
  if (n == 7) {
   return;
  } else {
   queen(n + 1);
  }
 }
}