#define RED 1
#define YELLOW 5
#define GREEN 13
void setup(){
  pinMode(RED,OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(GREEN,OUTPUT);
}
void loop(){
  digitalWrite(YELLOW,HIGH);
  digitalWrite(RED,LOW);
  digitalWrite(GREEN,LOW);
  delay(500);
  digitalWrite(RED, HIGH);
  digitalWrite(YELLOW, LOW);
  digitalWrite(GREEN,LOW);
  delay(500);
  digitalWrite(GREEN,HIGH);
  digitalWrite(RED,LOW);
  digitalWrite(YELLOW,LOW);
  delay(500);
}