int valor;
void setup()
{
  pinMode(8, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(2, OUTPUT);
}
void loop()
{
  valor = analogRead(A0);
  if (valor < 250) {
    digitalWrite(6, LOW);
    digitalWrite(4, LOW);
    digitalWrite(2, LOW);
    digitalWrite(8, LOW);
  }
  if (valor > 250 and valor < 500) {
    digitalWrite(6, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(2, LOW);
    digitalWrite(8, LOW);
  }
  if (valor > 500 and valor < 750) {
    digitalWrite(6, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(2, LOW);
    digitalWrite(8, LOW);
  }
  if (valor > 750) {
    digitalWrite(6, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(2, HIGH);
    digitalWrite(8, HIGH);
  }
}