void setup() {
  // put your setup code here, to run once:
 pinMode(A0, OUTPUT);
 pinMode(A1, OUTPUT);
 pinMode(A2, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(A0, HIGH);
digitalWrite(A1, LOW);
digitalWrite(A2, LOW);
delay(1000);
digitalWrite(A0, LOW);
digitalWrite(A1, HIGH);
digitalWrite(A2, LOW);
delay(1000);
digitalWrite(A0, HIGH);
digitalWrite(A1, LOW);
digitalWrite(A2, LOW);
delay(1000);
}