const int numLED=4;
const int pinLED[numLED]={8,9,10,11};     
void setup () {
  for (int i=0; i<4; i++){
    pinMode(pinLED[i], OUTPUT);
  }
}
void loop() {
  for(int i=0;i<3; i++){
    digitalWrite(pinLED[i], HIGH);
    delay(200);
    digitalWrite(pinLED[i], LOW);
  }
  for(int i=3;i>0; i--){
    digitalWrite(pinLED[i], HIGH);
    delay(200);
    digitalWrite(pinLED[i], LOW);
  }
}