const int kPinLed1 = 2; 
const int kPinLed2 = 3; 
const int kPinLed3 = 4;
const int kPinLed4 = 5;
void setup() {
  // put your setup code here, to run once:
pinMode(kPinLed1, OUTPUT);
pinMode(kPinLed2, OUTPUT);
pinMode(kPinLed3, OUTPUT);
pinMode(kPinLed4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
// turn on each of the LEDs in order
digitalWrite(kPinLed1, HIGH);
delay(100);
digitalWrite(kPinLed2, HIGH);
delay(100);
digitalWrite(kPinLed3, HIGH);
delay(100);
digitalWrite(kPinLed4, HIGH);
delay(100);
// turn off each of the LEDs in order
digitalWrite(kPinLed1, LOW);
delay(100);
digitalWrite(kPinLed2, LOW);
delay(100);
digitalWrite(kPinLed3, LOW);
delay(100);
digitalWrite(kPinLed4, LOW);
delay(100);
}