int led1 =8, led2=9, led3=10;

void setup() {
  
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
}

void loop() {
  digitalWrite(led1, HIGH); 
  digitalWrite(led2, HIGH);
  digitalWrite(led3, HIGH);
  delay(500);                    
  digitalWrite(led1, LOW);  
  delay(500);             
  digitalWrite(led2, LOW);
  delay(500);
  digitalWrite(led3, LOW);
  delay(500);      
}