#define led1 3
#define led2 6
#define led3 9
#define led4 10



void setup() {
  // put your setup code here, to run once:
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  for(int i=2;i<=10;i++){
    digitalWrite(i, HIGH);
    delay(500);

  }
  for(int i=10;i>=2;i--){
    digitalWrite(i, LOW);
    delay(500);
  }


}