const int trigpin = 4;
const int echopin = 2;

int duration;
int distance;

void setup() {
pinMode (trigpin, OUTPUT);
pinMode (echopin, INPUT);
Serial.begin (9600);

}

void loop() {
digitalWrite (trigpin, HIGH);
delayMicroseconds(10);
digitalWrite (trigpin, LOW);
delayMicroseconds (10);
digitalWrite (trigpin, LOW);
duration = pulseIn (echopin, HIGH);
distance = duration * 0.034/2 ;

Serial.print ("Distance=");
Serial.println (distance);

}