int LED [5] = {2, 3, 4, 5, 6};
void setup() {
  // put your setup code here, to run once:
 for (int i=0 ; i<sizeof(LED)/sizeof(int); i=i+1){
  pinMode(LED[i], OUTPUT);
 }
}

void loop() {
  // put your main code here, to run repeatedly:
 for (int i=0 ; i<sizeof(LED)/sizeof(int); i=i+1){
  digitalWrite(LED[i], HIGH);
  delay (200);
  digitalWrite(LED[i], LOW);
  delay (200);
 }

  for (int i=3 ; i>0; i=i-1){
  digitalWrite(LED[i], HIGH);
  delay (200);
  digitalWrite(LED[i], LOW);
  delay (200);
 }
}