#include <LiquidCrystal.h>

const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

int btnsum = 0;
int btnminus = 1;
int btnzero = 6;
int btnpote = 7;
int a = 0;
int lastBtnpoteState = HIGH; 

void setup() {
  lcd.begin(16, 2);
  pinMode(btnsum, INPUT_PULLUP);
  pinMode(btnminus, INPUT_PULLUP);
  pinMode(btnzero, INPUT_PULLUP);
  pinMode(btnpote, INPUT_PULLUP);
}

void loop() {
  lcd.setCursor(0, 0);
  lcd.print(a);

  int btnpoteState = digitalRead(btnpote);
  if (btnpoteState == LOW && lastBtnpoteState == HIGH) {
    a = analogRead(A0); 
    delay(200);
  }

  lastBtnpoteState = btnpoteState; 

  if (digitalRead(btnsum) == LOW) {
    a++;
    delay(200);
  }
  if (digitalRead(btnminus) == LOW) {
    a--;
    delay(200);
  }
  if (digitalRead(btnzero) == LOW) {
    a = 0;
    delay(200);
  }

  lcd.print("  ");
  delay(200);
}