int LED1 = 2;
int LED2 = 15;
int LED3 = 4;
int LED4 = 5;

void setup() {
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
  Serial.begin(9600);
  Serial.println("Hello, ESP32!");
}

void loop() {
  digitalWrite(LED1, HIGH);
  delay(500);
  digitalWrite(LED1, LOW);
  delay(500);
  digitalWrite(LED2, HIGH);
  delay(500);
  digitalWrite(LED2, LOW);
  delay(500);
  digitalWrite(LED3, HIGH);
  delay(500);
  digitalWrite(LED3, LOW);
  delay(500);
  digitalWrite(LED4, HIGH);
  delay(500);
  digitalWrite(LED4, LOW);
  delay(500);
}