const int redLED = 4;
const int yelloLED = 5;
const int greenLED = 6;

void setup()
{
pinMode(redLED, OUTPUT);
pinMode(yelloLED, OUTPUT);
pinMode(greenLED, OUTPUT);
}

void loop()
{
 
flash(redLED, 500);
flash(yelloLED, 500);
flash(greenLED, 500);
 
}
void flash(int pin, int wait)
{
 digitalWrite(pin, HIGH);
 delay(wait);
  digitalWrite(pin, LOW);
 delay(wait);
  
}