void setup()
{
  Serial.begin(115200);
  pinMode(13, INPUT);
  pinMode(19, OUTPUT);
  pinMode(18, OUTPUT);
}

void loop() 
{
  int a=analogRead(13);
  Serial.println("The value of the potentiometer is "+String(a));
  if(a>=0 && a<=499)
  {
    digitalWrite(18, LOW);
    digitalWrite(19, HIGH);
  }
  else if(a>=500 && a<=1000)
  {
    digitalWrite(19, LOW);
    digitalWrite(18, HIGH);
  }
  else{
    digitalWrite(19, LOW);
    digitalWrite(18, LOW);
  }
}