void setup() {
  // put your setup code here, to run once:
pinMode(2, OUTPUT);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(2, HIGH);
delayMicroseconds(15);
digitalWrite(2, LOW);
int length = pulseIn(3,HIGH);
Serial.println(length/148.0);
delay(100);
}