#include <Keypad.h>
#include <LiquidCrystal.h>


LiquidCrystal lcd(0,1,2,3,4,5);
byte row=4;
byte col=4;
char key[4][4]={
  {'1','2','3','+'},
  {'4','5','6','-'},
  {'7','8','9','*'},
  {'C','0','E','/'}
  };
byte rowpin[4]={6,7,8,9};
byte colpin[4]={10,11,12,13};
Keypad mykeypad=Keypad(makeKeymap(key),rowpin,colpin,row,col);

long num1=0;
long num2=0;
double total=0;

void setup() {
  lcd.begin(16,2);
  lcd.print("Enter A NUmber");
  delay(1000);
  lcd.clear();
}

void loop() {
  char value=mykeypad.getKey();
  switch (value)
  {
    case '0'...'9':
    lcd.setCursor(0,0);
    num1=num1*10+(value-'0');
    lcd.print(num1);
    break;

    case '+':
    num1=(total!=0?total:num1);
    lcd.print('+');
    num2=secondNumber();
    total=num1+num2;
    lcd.setCursor(0,1);
    lcd.print(total);
    num1=num2=0;
    break;

    case '-':
    num1=(total!=0?total:num1);
    lcd.print('-');
    num2=secondNumber();
    total=num1-num2;
    lcd.setCursor(0,1);
    lcd.print(total);
    num1=num2=0;
    break;

    case '*':
    num1=(total!=0?total:num1);
    lcd.print('*');
    num2=secondNumber();
    total=num1*num2;
    lcd.setCursor(0,1);
    lcd.print(total);
    num1=num2=0;
    break;

    case '/':
    num1=(total!=0?total:num1);
    lcd.print('/');
    num2=secondNumber();
    total=num1/num2;
    lcd.setCursor(0,1);
    lcd.print(total);
    num1=num2=0;
    break;

    case 'C':
    total=num1=num2=0;
    lcd.clear();
    break;
  }
long secondNumber() {

  while(1) 
  {
    char value=mykeypad.getKey();
    if (value>='0' && value<='9')
    {
      num2=num2*10+(value-'0');
      lcd.setCursor(7,0);
      lcd.print(num2);
    }
    if (value=='E')
    break;
  }
  return(num2);
}