if (c2 >= d2 + 1) {
  for (int c0 = a1; c0 <= b1; c0 += 1)
    for (int c1_0 = c1; c1_0 <= d1; c1_0 += 1)
      s0(c0, c1_0);
} else {
  for (int c0 = a1; c0 <= min(b1, a2 - 1); c0 += 1)
    for (int c1_0 = c1; c1_0 <= d1; c1_0 += 1)
      s0(c0, c1_0);
  for (int c0 = a2; c0 <= b2; c0 += 1) {
    if (a1 >= c0 + 1) {
      for (int c1_0 = c2; c1_0 <= d2; c1_0 += 1)
        s1(c0, c1_0);
    } else if (c0 >= b1 + 1) {
      for (int c1_0 = c2; c1_0 <= d2; c1_0 += 1)
        s1(c0, c1_0);
    } else {
      for (int c1_0 = c2; c1_0 <= min(c1 - 1, d2); c1_0 += 1)
        s1(c0, c1_0);
      for (int c1_0 = c1; c1_0 <= min(d1, c2 - 1); c1_0 += 1)
        s0(c0, c1_0);
      for (int c1_0 = max(c1, c2); c1_0 <= min(d1, d2); c1_0 += 1) {
        s0(c0, c1_0);
        s1(c0, c1_0);
      }
      for (int c1_0 = max(max(c1, d1 + 1), c2); c1_0 <= d2; c1_0 += 1)
        s1(c0, c1_0);
      for (int c1_0 = max(c1, d2 + 1); c1_0 <= d1; c1_0 += 1)
        s0(c0, c1_0);
    }
  }
  for (int c0 = max(max(a1, a2), b2 + 1); c0 <= b1; c0 += 1)
    for (int c1_0 = c1; c1_0 <= d1; c1_0 += 1)
      s0(c0, c1_0);
}