const int Switch = A0;

void setup() 
{
  int b;
  pinMode(Switch,INPUT);

  for(b=0;b<=7;b++)
  {
    pinMode(b,OUTPUT);
    digitalWrite(b,HIGH);
  }
}

void loop() 
{
  static int a;
  
  if(digitalRead(Switch)==1)
  {
    for(a=0;a<=7;a++)
    {
      digitalWrite(a,LOW);
      delay(100);
      digitalWrite(a,HIGH);
    }
  }
  if(digitalRead(Switch)==0)
  {
    for(a=7;a>=0;a--)
    {
      digitalWrite(a,LOW);
      delay(100);
      digitalWrite(a,HIGH);
    }
  }
}