const int second = 50;

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

  for(int i=13;i>=6;i--){
  pinMode(i,OUTPUT);
  }
}

void up(int led,int second) {
  digitalWrite(led,HIGH);
  delay(second);
}

void down(int led,int second) {
  digitalWrite(led,LOW);
  delay(second);
}

void loop() {
  // put your main code here, to run repeatedly:
  for(int j=13;j>=6;j--){
    up(j,second);
  }

  for(int j=13;j>=6;j--){
    down(j,second);
  }
}