const int led_pin1 = 13;
const int led_pin2 = 12;
const int led_pin3 = 11;

void setup() {
  pinMode(led_pin1, OUTPUT);
  pinMode(led_pin2, OUTPUT);
  pinMode(led_pin3, OUTPUT);

}

void loop() {
  digitalWrite(led_pin1, HIGH);
  digitalWrite(led_pin2, LOW);
  digitalWrite(led_pin3, LOW);
  delay(250);
  digitalWrite(led_pin1, LOW);
  digitalWrite(led_pin2, HIGH);
  digitalWrite(led_pin3, LOW);
  delay(250);
  digitalWrite(led_pin1, LOW);
  digitalWrite(led_pin2, LOW);
  digitalWrite(led_pin3, HIGH);
  delay(250);
  digitalWrite(led_pin1, LOW);
  digitalWrite(led_pin2, HIGH);
  digitalWrite(led_pin3, LOW);
  delay(250);
}