long duration,cm;

void setup(){
  pinMode(10, OUTPUT);
  pinMode(11, INPUT);
  Serial.begin(9600);
  }

void loop(){
  digitalWrite(11, LOW);
  delayMicroseconds(2);
  digitalWrite(11, HIGH);
  delayMicroseconds(10);
  digitalWrite(11, LOW);
  duration = pulseIn(11, HIGH);
  cm=duration/29/2;

  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  delay(500);
}