int down = 1;
int up = 5;
int right = 0;
int left = 4;

void setup() {
   pinMode(down, INPUT_PULLUP);
   pinMode(up, INPUT_PULLUP);
   pinMode(right, INPUT_PULLUP);
   pinMode(left, INPUT_PULLUP);
   Serial.swap(1);
   Serial.begin(115200);
   }

void loop() {

  if(digitalRead(down) == LOW){
    Serial.println("Direction: DOWN");
  }
  else if(digitalRead(up) == LOW){
    Serial.println("Direction: UP");
  }
  else if(digitalRead(right) == LOW){
    Serial.println("Direction: RIGHT");
  }
  else if(digitalRead(left) == LOW){
    Serial.println("Direction: LEFT");
  }
  else{
    Serial.println("STOP");
  }
  delay(100);
}