---

const int trigPin = 9;
const int echoPin = 8;
const int ledPin = 13;
cinst int buzzerPin = 10;
const int distanceThreshold = 50;

void setup() {
  pinmode(trigPin, OUTPUT);
  pinmode(echoPin, INPUT);
  pinmode(trigPin, OUTPUT);
  pinmode(trigPin, OUTPUT);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  int duration = pulseIn(echoPin, HIGH);
  int distance = duration * 0.034 / 2;
  if (distance > 0 && distance <= distanceThreshold) {
    digitalWrite(ledPin, LOW);
    tone(buzzerPin, 1000);
    delay(200);
    digitalWrite(ledPin, LOW);
    noTone(buzzerPin);
  }else {
    digitalWrite(ledPin, LOW);
    noTone(buzzerPin);
  }
}