void setup() {
  // put your setup code here, to run repeatedly:
for(int i=2;i<=13;i++){
  pinMode(i, OUTPUT);
}


}


void loop() {
  // put your main code here, to run repeatedly:
for(int i=2; i<=13; i++){
  digitalWrite(i, HIGH);
  delay(100);
  digitalWrite(i, LOW);
}
  for(int i=13; i>=2; i--){
  digitalWrite(i, HIGH);
  delay(100);
  digitalWrite(i, LOW);
  }
  
}