#include <NewPing.h>// including Library for ultrasonic sensor
int triggerPin = 4; 
#define echoPin 3
#define maxDistance 400
NewPing varName(triggerPin, echoPin, maxDistance);
//LibraryName varName(pin no. or name of the pin no.)
void setup() {
  Serial.begin(9600);
   
}

void loop() {
  delay(300);
  unsigned int dist = varName.ping_cm();
  //ping_cm() is the Library function of NewPing library  
  // 
  Serial.print(dist);
  Serial.println("cm");
 
}