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

void loop()
{
  digitalWrite(11, LOW);
  delayMicroseconds(2);
  digitalWrite(11, HIGH);
  delayMicroseconds(10);
  digitalWrite(11, LOW);
  duration = pulseIn(10,HIGH);
  cm=duration/29/2;
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  delay(500);
}