int trig = 5;
int echo =  18;
int duration;
int distance;

void setup()
{
 Serial.begin(115200);
 pinMode(trig, OUTPUT);
 pinMode(echo, INPUT);
 }

 void loop()
 {
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH);
  distance = duration*0.034/2;
  Serial.println(distance);
  delay(100);
 }