var chap_array = new Array(
    ["17 - Mysterious Athletic Festival",'17'],

    ["16 - Mysterious Sea-Bathing",'16'],

    ["15 - Mysterious Step Up",'15'],

    ["14 - Mysterious Rain Shelter",'14'],

    ["13 - Mysterious Dessert",'13'],

    ["12 - Mysterious Memory",'12'],

    ["11 - Mysterious Arousal",'11'],

    ["10 - Mysterious Wonder Drug",'10'],

    ["9 - Mysterious Sign",'9'],

    ["8 - Mysterious Girl meets Mysterious Girl Continued",'8'],

    ["7 - Mysterious Girl Meets Mysterious Girl",'7'],

    ["6 - Mysterious Summer Vacation",'6'],

    ["5 - Mysterious Outdoor Pool",'5'],

    ["4 - Mysterious Day When the Wind was Strong",'4'],

    ["3 - Mysterious Test Tube",'3'],

    ["2 - Mysterious Photograph",'2'],

    ["1 - Mysterious Bond",'1'],

    ["0 - Mysterious Girlfriend X",'0']
);
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]);
    }
}