void setup() 
{
 for(int i = 2 ; i <= 8 ; i++) pinMode(i,HIGH); 
} 

void loop() 
{ 
  digitalWrite(2,HIGH); 
  for(int i = 1 ; i <= 8; i += 2) { 
  digitalWrite(i,HIGH); 
  digitalWrite(i+1,HIGH); 
  delay(1000); 
  }   
  
  for(int i = 8 ; i >= 3 ; i -= 2) { 
  digitalWrite(i,LOW); 
  digitalWrite(i-1, LOW); 
  delay(1000); 
  } 
}