#define TRIG_PIN 10
#define ECHO_PIN 9
#define RED_LED 3
#define GREEN_LED 5
#define YELLOW_LED 6

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  long duration, distance;

  
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
 
  duration = pulseIn(ECHO_PIN, HIGH);

  distance = (duration / 2) / 29.1;

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

 
  if (distance > 250) {
    digitalWrite(RED_LED, HIGH);
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, LOW);
  } else if (distance >= 100 && distance <= 250) {
    digitalWrite(RED_LED, LOW);
    digitalWrite(GREEN_LED, HIGH);
    digitalWrite(YELLOW_LED, LOW);
  } else if (distance < 100) {
    digitalWrite(RED_LED, LOW);
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, HIGH);
  } else {
    
    digitalWrite(RED_LED, LOW);
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, LOW);
  }

  
  delay(500);
}