void setup() {
  // put your setup code here, to run once:

for(int i=0;i<=3;i++){
  pinMode(i, OUTPUT);
}
}

void loop() {

for(int i=0;i<=3;i++){
  digitalWrite(i, HIGH);
  delay(177);

}
  // put your main code here, to run repeatedly:

  for (int i=3;i>=0;i--){
    digitalWrite(i, LOW);
  delay(177);
  }


  


 


}