int led1_3 = 2;
int led2_4 = 15;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(led1_3, OUTPUT);
  pinMode(led2_4, OUTPUT);
}

void loop() {
  for(int i=0; i<=10000;i=i+30){
    digitalWrite(led1_3, HIGH);
    delay(i);
    digitalWrite(led1_3, LOW);
    delay(i);
    digitalWrite(led2_4, HIGH);
    delay(i);
    digitalWrite(led2_4, LOW);
    delay(i);
  }
}