int led[5]={7,8,9,10,11};

void setup(){
  for(int i=0; i<=4; i++){
  pinMode(led[i],OUTPUT);
  }
}

void loop(){
  for(int i=0; i<=4; i++){
  digitalWrite(led[i],HIGH);
  delay(500);
  digitalWrite(led[i],LOW);
  delay(500);
  }
  
  for(int i=3; i>=1; i--){
  digitalWrite(led[i],HIGH);
  delay(500);
  digitalWrite(led[i],LOW);
  delay(500);
  }
}