void setup() {
  // put your setup code here, to run once:
pinMode(7, OUTPUT);
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(1, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(7, HIGH);
delay(500);
digitalWrite(7, LOW);
delay(500);
digitalWrite(3, HIGH);
delay(500);
digitalWrite(3, LOW);
delay(500);
digitalWrite(4, HIGH);
delay(500);
digitalWrite(4, LOW);
delay(500);
digitalWrite(1, HIGH);
delay(500);
digitalWrite(1, LOW);
delay(500);
}