const int analogInputPin = A0; 
const int redLedPin = 9; 
const int yellowLedPin = 10; 
const int greenLedPin = 11;
int sensorValue = 0;




void setup() {
  // put your setup code here, to run once:
Serial.begin (9600);
  pinMode (analogInputPin , INPUT);
    pinMode(redLedPin, OUTPUT);
      pinMode(yellowLedPin, OUTPUT);
        pinMode(greenLedPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
int sensorValue = analogRead(analogInputPin); 
Serial.println(sensorValue);
  if (sensorValue < 100) {
      digitalWrite(redLedPin, HIGH);
          digitalWrite(yellowLedPin, LOW);
              digitalWrite(greenLedPin, LOW);
                } else if (sensorValue >= 100 && sensorValue < 500) {
                    digitalWrite(redLedPin, LOW);
                        digitalWrite(yellowLedPin, HIGH);
                            digitalWrite(greenLedPin, LOW);
                              } else {
                                  digitalWrite(redLedPin, LOW);
                                      digitalWrite(yellowLedPin, LOW);
                                          digitalWrite(greenLedPin, HIGH);
                                            }
                                           }