void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(5, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(18, OUTPUT);
  pinMode(19, OUTPUT);
  pinMode(13, INPUT);
}

void loop() {
  int btn = digitalRead(13);

  if(btn==0) {
    digitalWrite(5, LOW);
    digitalWrite(4, LOW);
    digitalWrite(18, LOW);
    digitalWrite(19, LOW);
  }

  if(btn==1) {
    if(digitalRead(5)==LOW) {
    digitalWrite(5, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(18, HIGH);
    digitalWrite(19, LOW);
    } else if(digitalRead(4)==LOW) {
    digitalWrite(5, LOW);
    digitalWrite(4, HIGH);
    digitalWrite(18, LOW);
    digitalWrite(19, HIGH);
    }
    delay(1000);
  }
}