const int GP1 = 4;
const int GP2 = 9;
const int GP3 = 12;
void setup() {
pinMode(GP1, OUTPUT);
pinMode(GP2, OUTPUT);
pinMode(GP3, OUTPUT);
}
void loop() {
digitalWrite(GP1, HIGH);
delay(500);
digitalWrite(GP1, LOW);
delay(500);
digitalWrite(GP2, HIGH);
delay(500);
digitalWrite(GP2, LOW);
delay(500);
digitalWrite(GP3, HIGH);
delay(500);
digitalWrite(GP3, LOW);
delay(500);
}