int P = A0;
int R = 10;
int Y = 9;
int G = 8;
int val = 0;

void setup() {
  pinMode(R, OUTPUT);
  pinMode(Y, OUTPUT);
  pinMode(G, OUTPUT);
}

void loop() {
  val = analogRead(P);
  if (410 > val) {
    digitalWrite(R, HIGH);
  } else {
    digitalWrite(R, LOW);
  }


  if (819 > val && val > 410) {
    digitalWrite(Y, HIGH);
  } else {
    digitalWrite(Y, LOW);
  }

  if (val > 819) {
    digitalWrite(G, HIGH);
  } else {
    digitalWrite(G, LOW);
  }
}