#include <LiquidCrystal_I2C.h> 
#define BTN1 5
#define BTN2 4

LiquidCrystal_I2C lcd(0x27,16,2);

int a = 0; // кількість молока
float result = 0;
const float percentage = 9.00;

void setup() {
  lcd.init();
  lcd.clear();        
  lcd.backlight();

  pinMode(BTN1, INPUT_PULLUP);
  pinMode(BTN2, INPUT_PULLUP);
  lcd.setCursor(0,0);
  lcd.print("Press red button");
}

void loop() {
  if(digitalRead(BTN1)==LOW){
    lcd.clear(); 
    lcd.setCursor(0,0);
    lcd.print("Input milk mass");
    delay(500);
    a = a + 1;
    lcd.setCursor(0,1);
    lcd.print(String(a) + "kg");
  }

  if(digitalRead(BTN2)==LOW){
    result = a * percentage / 100;
    lcd.clear(); 
    lcd.setCursor(0,0);
    lcd.print(String(result) + "kg");
  }

}