int led1 = 3;
int led2 = 2;
int led3 = 4;


void setup(){
  // put your setup code here, to run once:
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);

}

void loop(){
  // put your main code here, to run repeatedly:
  digitalWrite(led1, HIGH);
    delay(500);

  digitalWrite(led2, HIGH);
    delay(1000);

  digitalWrite(led3, HIGH);
  delay(1500);

  digitalWrite(led1, LOW);
    delay(1000);

  digitalWrite(led2, LOW);
    delay(500);

  digitalWrite(led3, LOW);
     delay(1500);

}