#define REDPIN 23
#define YELLOWPIN 22
#define GREENPIN 21

void setup() {
  
  pinMode(REDPIN, OUTPUT);
  pinMode(YELLOWPIN, OUTPUT);
  pinMode(GREENPIN, OUTPUT);
}

void loop() {

  digitalWrite(REDPIN, HIGH);
  digitalWrite(YELLOWPIN, LOW);
  digitalWrite(GREENPIN, LOW);
  delay(1000);

  
  digitalWrite(REDPIN, LOW);
  digitalWrite(YELLOWPIN, HIGH);
  digitalWrite(GREENPIN, LOW);
  delay(1000);

 
  digitalWrite(REDPIN, LOW);
  digitalWrite(YELLOWPIN, LOW);
  digitalWrite(GREENPIN, HIGH);
  delay(1000);

  
}