Workplz

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);

#define trigPin 13
#define echoPin 12
int counter = 0;
int currentState = 0;
int previousState = 0;
void setup() {



 Serial.begin (9600);
 pinMode(trigPin, OUTPUT);
 pinMode(echoPin, INPUT);
}

void loop() {

lcd.begin(16,2); // sixteen characters across - 2 lines
  // first character - 1st line
  lcdbacklight();
  lcd.setCursor(0,0);
  lcd.print(counter);
  lcd.clear();
  lcd.print(counter);


 long duration, distance;
 digitalWrite(trigPin, LOW);
 delayMicroseconds(1000);
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(1000);
 digitalWrite(trigPin, LOW);
 duration = pulseIn(echoPin, HIGH);
 distance = (duration/1) / 29.1;
 if (distance <= 10){
 currentState = 1;
 }
 else {
 currentState = 0;
 }
 delay(500);
 if(currentState != previousState){
if(currentState == 1){
counter = counter + 1;
Serial.println(counter);
}
}
}