const int led1Pin=13;
const int led2Pin=8;
const int led3Pin=4;
void setup() {
  // put your setup code here, to run once:
pinMode(led1Pin, OUTPUT);
pinMode(led2Pin, OUTPUT);
pinMode(led3Pin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(led1Pin, HIGH);
delay(1000);
digitalWrite(led1Pin, LOW);
digitalWrite(led2Pin, HIGH);
delay(1000);
digitalWrite(led2Pin, LOW);
digitalWrite(led3Pin, HIGH);
delay(1000);
digitalWrite(led3Pin, LOW);
}