int trigPin = 9;
int echoPin = 10;

int greenLED = 2;
int redLED = 3;

int buzzer = 4;

long duration;
int distance;

void setup() {

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  pinMode(greenLED, OUTPUT);
  pinMode(redLED, OUTPUT);

  pinMode(buzzer, OUTPUT);

  Serial.begin(9600);
}

void loop() {

  // Send ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);

  digitalWrite(trigPin, LOW);

  // Receive echo
  duration = pulseIn(echoPin, HIGH);

  // Calculate distance
  distance = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Parking logic
  if (distance < 20) {

    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);

     noTone(buzzer);

  } else {

    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH);
    tone(buzzer, 1000);

   
  }

  delay(500);
}