Ultrasonic Sensor don't work

My ultrasonic sensor (HC-SR04) don't works. It always print 0 cm not matter what I put in front of it. I've checked the trig pin and I can confirm that it is sending signals.

My code:

int trig = 3;
int echo = 2;
int pie = 4;

double cm;
int dur;

void setup()
{
  Serial.begin(9600);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(pie, OUTPUT);
}

void loop()
{
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  
  dur = pulseIn(echo, HIGH);
  
  cm = dur * 0.034 / 2;
  
  if (cm <= 200){
    tone(pie, 262, 500);
  }
  
  Serial.println(cm);
  
  delay(200);
}

I am using an Arduino Mega

Will attach a picture later

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