#define LEDYELOW 5
#define LEDRED 18
#define LEDGREEN 19

void setup() {
  pinMode(LEDYELOW, OUTPUT);
  pinMode(LEDRED, OUTPUT);
  pinMode(LEDGREEN, OUTPUT);
 
}

void loop() {
 digitalWrite(LEDYELOW, LOW);
 delay(500);
 digitalWrite(LEDYELOW, HIGH);
 delay(500);
 digitalWrite(LEDRED, LOW);
 delay(500);
 digitalWrite(LEDRED, HIGH);
 delay(500);
 digitalWrite(LEDGREEN, LOW);
 delay(500);
 digitalWrite(LEDGREEN, HIGH);
 
}