const int trigPin = 9;
const int echoPin = 10;
long duration;
int distanceCm;

void setup() {
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
Serial.begin(9600);
}

void loop() {
  
digitalWrite(trigPin,HIGH);

delayMicroseconds(10);

digitalWrite(trigPin,LOW);

duration = pulseIn(echoPin, HIGH);
distanceCm= duration*0.034/2;
if(distanceCm>300){
  distanceCm=0;
}
Serial.println(distanceCm);
delay(50);
}