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

LiquidCrystal lcd(5,4,A0,A1,A2,A3);

  char keys[4][4] = {
              {'1','2','3','+'},
              {'4','5','6','-'},
              {'7','8','9','*'},
              {'*','0','=','/'}
            };
  
  byte rowsPin[4] = {13,12,11,10};
  byte colsPin[4] = {9,8,7,6};

Keypad pad = Keypad(makeKeymap(keys),rowsPin,colsPin,4,4);
void setup() {
  // put your setup code here, to run once:

  pinMode(5, OUTPUT);

  Serial.begin(9600);

  lcd.begin(16,2);
}
String s1="";
void loop() {
  // put your main code here, to run repeatedly:

  char c = pad.getKey();
  if(c != NO_KEY){
    //Serial.print(c);
    lcd.print(c);
    s1=s1+c;
    Serial.println(s1);
    if(s1.indexOf("=") != -1){
    Calc();
    }
  }
  
}

void Calc(){
  int plus = s1.indexOf('+');
  // int p = plus.toInt();
  if(plus != -1){

    int num1 = s1.substring(0, plus);
    // int num2 = s1.substring(plus + 1);
    Serial.println(num1);
    // int n1 = Int(num1);
    // int n2 = num2.toInt();
    // lcd.print(n1+n2);

  }

}