#define Buzzer 12
#define LED_RED 13
#define ECHO_PIN A0
#define TRIG_PIN 11

void setup() {
  pinMode(Buzzer, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  Serial.begin(115200);
}

void loop() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(11);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int distance = (pulseIn(ECHO_PIN, HIGH) / 29) / 11;
  Serial.println(distance);
  if (distance <= 50) {
    digitalWrite(13, HIGH);
    digitalWrite(Buzzer, HIGH);
    delay(100);
  } else {
    digitalWrite(13, LOW);
    digitalWrite(Buzzer, LOW);
    delay(100);
  }
}