void setup() {
  pinMode(16, OUTPUT);
  pinMode(17, OUTPUT);
  pinMode(18, OUTPUT);
  pinMode(19, OUTPUT);

  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
}

void loop() {
  digitalWrite(16, LOW);
  digitalWrite(16, HIGH);
  delay(1000);
  digitalWrite(16, LOW);

  digitalWrite(17, LOW);
  digitalWrite(17, HIGH);
  delay(1000);
  digitalWrite(17, LOW);

  digitalWrite(18, LOW);
  digitalWrite(18, HIGH);
  delay(1000);
  digitalWrite(18, LOW);

  digitalWrite(19, LOW);
  digitalWrite(19, HIGH);
  delay(1000);
  digitalWrite(19, LOW);
}