int leds[]={23,22,21,19,18,17};
void setup(){
  for(int i=0;i<=5;i++){
    pinMode(leds[i],OUTPUT);
    digitalWrite(leds[i],LOW);
  }
}

void loop(){
  for (int i = 0; i <= 5; i++) {
    digitalWrite(leds[i],HIGH);
    delay(500);
    digitalWrite(leds[i],LOW);
     delay(500);
  }

}