float val = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(A0, INPUT);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  val = (analogRead(A0)/1024.)*5;
  if(val < 1){
    ledState(LOW, LOW, LOW, LOW);
  }
  else if(val > 1 && val < 2){
    ledState(HIGH, LOW, LOW, LOW);
  }
  else if(val > 2 && val < 3){
    ledState(HIGH, HIGH, LOW, LOW);
  }
  else if(val > 3 && val < 4){
    ledState(HIGH, HIGH, HIGH, LOW);
  }
  else if(val > 4 && val < 5){
    ledState(HIGH, HIGH, HIGH, HIGH);
  }
  //Serial.println(val);
  //delay(1000);
}

void ledState(int a, int b, int c, int d){
    digitalWrite(2, a);
    digitalWrite(3, b);
    digitalWrite(4, c);
    digitalWrite(5, d);
}