#include <LiquidCrystal.h>

const int trigger = 2;
const int echo = 3;

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

void setup() {
  lcd.begin(16, 2);
}

void loop() {
  long duration, cm;
  pinMode(trigger, OUTPUT);

  digitalWrite(trigger, LOW);
  delay(2);

  digitalWrite(trigger, HIGH);
  delay(10);

  digitalWrite(trigger, LOW);

  pinMode(echo, INPUT);

  duration = pulseIn(echo, HIGH);
  cm = microsecondsToCentimeters(duration);

  lcd.clear();
  lcd.print(cm);
}

long microsecondsToCentimeters(long microseconds){
  return microseconds /29 / 2;
}