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);


}