void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(4, OUTPUT);
  pinMode(16, OUTPUT);
  pinMode(17, OUTPUT);
}

void loop() {
  digitalWrite(4, HIGH);
  delay(1000);
  digitalWrite(4, LOW);
  delay(1000);

  digitalWrite(16, HIGH);
  delay(1000);
  digitalWrite(16, LOW);
  delay(1000);

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