void setup() {
  for (int LED = 2; LED<=13; LED++){
    pinMode(LED, OUTPUT);
  }
}

   void loop() {
     for (int LED = 2; LED<=13; LED++){
       digitalWrite(LED, HIGH);
       delay (100);
       digitalWrite(LED, LOW);
     }
     for (int LED = 2; LED<=13; LED++){
       digitalWrite(LED, LOW);
       delay(50);
     }
     for (int LED = 13; LED>=2; LED--) {
       digitalWrite(LED, HIGH);
       delay (200);
       digitalWrite(LED, LOW);
     }
     for (int LED = 13; LED>=2; LED--){
       delay (50);
     }
   }