// C++ code
//
#include <LiquidCrystal.h>
const int RS=12, EM=11, D4=10, D5=9, D6=8, D7=7;
LiquidCrystal lcd(RS, EM, D4, D5, D6, D7);
int trig = 3;
int echo = 2;
int lecture_echo;
int dist;
int cars = 6;
void setup()
{
  pinMode(trig, OUTPUT);
  digitalWrite(trig, LOW);
  pinMode(echo, INPUT);
  lcd.begin(16,2);
  pinMode(13, OUTPUT);
  pinMode(4 , OUTPUT);
  pinMode(1, OUTPUT);
  pinMode(5, INPUT);
  pinMode(6,INPUT);
}

void loop()
{
  lcd.setCursor(0,0);
  lcd.print("Cars : ");
  lcd.print(cars);
  dist = getdistance();
  lcd.setCursor(12,1);
  lcd.print(dist);
  if(dist < 100){
    digitalWrite(13, HIGH);
    if (cars < 10){
      digitalWrite(4, HIGH);
      digitalWrite(1, LOW);
      if(digitalRead(5) == HIGH){
        delay(5000);
        cars = cars + 1;
      }
    }else{
      digitalWrite(4, LOW);
      digitalWrite(1, HIGH);
    }
  }else{
    digitalWrite(13, LOW);
  }
  if(digitalRead(6) == HIGH){
    delay(5000);
    cars = cars -1;
  }
}
int getdistance(){
  int distance;
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  lecture_echo = pulseIn(echo, HIGH);
  distance = lecture_echo / 58;
  return distance;
}