int ledPin1 = 12;
int ledPin2 = 13;

void setup() {
//letak pin led
pinMode(12, OUTPUT);
pinMode(13, OUTPUT);
}

void loop() {
//led hidup secara bergantian
digitalWrite(12, HIGH);
digitalWrite(13, LOW);
delay(800);
digitalWrite(13, HIGH);
digitalWrite(12, LOW);
delay(800);
}