var chap_array = new Array(
    ["50",'50'],

    ["49",'49'],

    ["48",'48'],

    ["47",'47'],

    ["46",'46'],

    ["45",'45'],

    ["44",'44'],

    ["43",'43'],

    ["42",'42'],

    ["41",'41'],

    ["40",'40'],

    ["39",'39'],

    ["38",'38'],

    ["37",'37'],

    ["36",'36'],

    ["35",'35'],

    ["34",'34'],

    ["33",'33'],

    ["32",'32'],

    ["31",'31'],

    ["30",'30'],

    ["29",'29'],

    ["28",'28'],

    ["27",'27'],

    ["26 - Volume5 Chapter6",'26'],

    ["25 - Volume5 Chapter5",'25'],

    ["24 - Volume5 Chapter4",'24'],

    ["23 - Volume5 Chapter3",'23'],

    ["22 - Volume5 Chapter2",'22'],

    ["21 - Volume5 Chapter1",'21'],

    ["20 - Volume4 Chapter6",'20'],

    ["19 - Volume4 Chapter5",'19'],

    ["18 - Volume4 Chapter4",'18'],

    ["17 - Volume4 Chapter3",'17'],

    ["16 - Volume4 Chapter2",'16'],

    ["15 - Volume4 Chapter1",'15'],

    ["14 - Volume3 Chapter5",'14'],

    ["13 - Volume3 Chapter4",'13'],

    ["12 - Volume3 Chapter4",'12'],

    ["11 - Volume3 Chapter2",'11'],

    ["10 - Volume3 Chapter1",'10'],

    ["9 - Volume2 Chapter5",'9'],

    ["8 - Volume2 Chapter4",'8'],

    ["7 - Volume2 Chapter3",'7'],

    ["6 - Volume2 Chapter2",'6'],

    ["5 - Volume2 Chapter1",'5'],

    ["4",'4'],

    ["3",'3'],

    ["2",'2'],

    ["1",'1']
);
for (var i=0; i<chap_array.length; i++) {
    document.getElementById('id_chapter_1').options[i] = new Option(chap_array[i][0],chap_array[i][1]);
    if (document.getElementById('id_chapter_2')) {
        document.getElementById('id_chapter_2').options[i] = new Option(chap_array[i][0],chap_array[i][1]);
    }
}