const int leds[] = {8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2}; 

void setup() {
    for (int i = 0; i < 12; i++) {
        pinMode(leds[i], OUTPUT); 
    }
}

void loop() {
    for (int i = 0; i < 12; i += 2) { 
        digitalWrite(leds[i], HIGH);
        digitalWrite(leds[i + 1], HIGH);
        delay(200); 
        digitalWrite(leds[i], LOW);
        digitalWrite(leds[i + 1], LOW);
    }
}