void setup () {
pinMode (3,OUTPUT);
pinMode (A0,INPUT);
Serial.begin(9600);
}
void loop () {
int a = analogRead (A0);
 Serial.print("nilai a = ");
 Serial.println(a);
 if(a > 500) {
  digitalWrite(2,HIGH);}
  else {digitalWrite (2,LOW);}
  if(a > 800){
   digitalWrite(3,HIGH);}
   else{digitalWrite(3,LOW);}
  if(a > 1000){
   digitalWrite(4,HIGH);}
   else{digitalWrite(4,LOW);}
}