// /**** sample *****/

  function addition(first = 0, second = 0) {
      var a = parseFloat(first);
      var b = parseFloat(second);
      var total = 0;
      total = a + b;
      return total;
  }

  function subtraction(first = 0, second = 0) {
      var a = parseFloat(first);
      var b = parseFloat(second);
      var sub = a - b;
      return sub;
  }

  function multiplication(first = 0, second = 0) {
      var a = parseFloat(first);
      var b = parseFloat(second);
      var product = a * b;

      return product;
  }

  function division(first = 0, second = 0) {
      var a = parseFloat(first);
      var b = parseFloat(second);
      var divi = a / b;
      return divi;
  }

  function get_exploded(result,operator){
    var holder = 0;
    if(result.length <= 1 ){
      holder = 0;
    }
    else if(result.length == 2){
      r1 = ((result[0]) ? result[0] : 0);
      if(isNaN(r1)){
        finder =  /(\*|\+|\*|\/|\-)/g;
        finder_result = result[0].match(finder);
        if(finder_result.length > 0){
          exploded_new = result[0].split(""+finder_result+"");
          r1_new = ((exploded_new[0]) ? exploded_new[0] : 0);
          r2_new = ((exploded_new[1]) ? exploded_new[1] : 0);
          r1 = process_operator(finder_result, r1_new, r2_new);
        }
      }
      holder = process_operator(operator, r1, 0);
    }
    else{
      r1 = ((result[0]) ? result[0] : 0);
      r2 = ((result[1]) ? result[1] : 0);
      holder = process_operator(operator, r1, r2);
    }
    return holder;
  }

  function process_operator(operator, r1, r2){
    var holder = 0;
    if(operator == '+'){
      holder =  addition(r1, r2);
    }
    else if(operator == '-'){
       holder =  subtraction(r1, r2);
    }
    else if(operator == '*'){
      if(r1 == 0 && r2 == 0){
        holder = 0;
      }
      else if(r1 > 0 && r2 == 0){
        holder = r1;
      }
      else if(r1 > 0 && r2 > 0){
        holder =  multiplication(r1, r2);
      }
      else{
        holder = 0;
      }
    }
    else if(operator == '/'){
      if(r1 == 0 && r2 == 0){
        holder = 0;
      }
      else if(r1 > 0 && r2 == 0){
        holder = r1;
      }
      else if(r1 > 0 && r2 > 0){
        holder =  division(r1, r2);
      }
      else{
        holder = 0;
      }
    }
    return holder;
  }

  function get_input(e){
    var input = $(this).val();
    if(e.which == 107){
      result = input.split("+");
      return $(this).val(get_exploded(result,'+')+'+');
    }
    else if(e.which == 106){
      result = input.split("*");
      return $(this).val(get_exploded(result,'*')+'*');
    }
    else if(e.which == 109){
      result = input.split("-");
      return $(this).val(get_exploded(result,'-')+'-');
    }
    else if(e.which == 111){
      result = input.split("/");
      return $(this).val(get_exploded(result,'/')+'/');
    }
    else if(e.which == 13){
      if(isNaN(input)){
        result[0] = input;
        result[1] = 0;
        check_operator = /(\*|\+|\*|\/|\-)/g;
        operator_result = result[0].match(check_operator);
        return $(this).val(get_exploded(result,operator_result));
      }
      else{
        return $(this).val(input);
      }
    }
  }

  $('input[type=text], input[type=number]').keyup(get_input);

  // /**** end sample***/