const int tri=13;
 const int echo=12;
 float distance;
 long dur;
 void setup(){
   Serial.begin(115200);
   pinMode(tri,OUTPUT);
   pinMode(echo,INPUT);
 }
 long getdistance()
 {
   digitalWrite(tri,LOW);
   delayMicroseconds(2);
   digitalWrite(tri,HIGH);
   delayMicroseconds(10);
   digitalWrite(tri,LOW);
   dur=pulseIn(echo,HIGH);
   return(dur*0.0034/2)+1;
   Serial.println(dur);
 }
 void loop()
 {
   distance-=getdistance();
   Serial.println("distance : " +String(distance));
   delay(10);
 }