int led1= 13;
int led2=12;
int led3=11;

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
}

void loop() {
  digitalWrite(led1, HIGH);
  delay(1000);
  digitalWrite(led1, LOW);
  delay(1000);
  digitalWrite(led2, HIGH);
  delay(1000);
  digitalWrite(led2, LOW);
  delay(1000);
  digitalWrite(led3, HIGH);
  delay(1000);
  digitalWrite(led3, LOW);
  delay(1000);
  digitalWrite(led3, HIGH);
  delay(1000);
  digitalWrite(led3, LOW);
  delay(1000);
  digitalWrite(led2, HIGH);
  delay(1000);
  digitalWrite(led2, LOW);
  delay(1000);
  digitalWrite(led1, HIGH);
  delay(1000);
  digitalWrite(led1, LOW);
  delay(1000);
}