const int redBUTTON = 1;
const int yellowBUTTON = 2;
const int greenBUTTON = 3;
const int redLED = 13;
const int yellowLED = 12;
const int greenLED = 11;

void setup() {
  pinMode(redBUTTON, INPUT_PULLUP);
  pinMode(yellowBUTTON, INPUT_PULLUP);
  pinMode(greenBUTTON, INPUT_PULLUP);
  pinMode(redLED, OUTPUT);
  pinMode(yellowLED, OUTPUT);
  pinMode(greenLED, OUTPUT);
  

}

void loop() {
  int redPB = digitalRead(redBUTTON),
  yellowPB = digitalRead(yellowBUTTON),
  greenPB = digitalRead(greenBUTTON);
  if (redPB == LOW) {
    digitalWrite(redLED, HIGH);
    digitalWrite(yellowLED, LOW);
    digitalWrite(greenLED, LOW);
  } else if (yellowPB == LOW) {
    digitalWrite(redLED, LOW);
    digitalWrite(yellowLED, HIGH);
    digitalWrite(greenLED, LOW);
  } else if(greenPB == LOW) {
    digitalWrite(redLED, LOW);
    digitalWrite(yellowLED, LOW);
    digitalWrite(greenLED, HIGH);
  }
}