var chapter_list = new Array(
  ["Vol.01 Ch.001","v01/c001"],
  ["Vol.01 Ch.002","v01/c002"],
  ["Vol.01 Ch.003","v01/c003"],
  ["Vol.01 Ch.004","v01/c004"],
  ["Vol.01 Ch.004.5: Extra - Christmas","v01/c004.5"],
  ["Vol.02 Ch.005","v02/c005"],
  ["Vol.02 Ch.006.1","v02/c006.1"],
  ["Vol.02 Ch.006.2","v02/c006.2"],
  ["Vol.02 Ch.007","v02/c007"],
  ["Vol.02 Ch.008","v02/c008"],
  ["Vol.02 Ch.008.5: Extra - Yes or Kiss","v02/c008.5"],
  ["Vol.03 Ch.009","v03/c009"],
  ["Vol.03 Ch.010","v03/c010"],
  ["Vol.03 Ch.011","v03/c011"],
  ["Vol.03 Ch.012","v03/c012"],
  ["Vol.03 Ch.012.1: SideStory","v03/c012.1"],
  ["Vol.03 Ch.012.2: Extra - Prologue","v03/c012.2"],
  ["Vol.04 Ch.004.1: Extra - Prologue","v04/c004.1"],
  ["Vol.04 Ch.004.2: Extra","v04/c004.2"]
);

var total_chapters = 19;

for (var i = 0; i < chapter_list.length; i++) {
  document.getElementById('top_chapter_list').options[i] = new Option(chapter_list[i][0], chapter_list[i][1]);
  document.getElementById('bottom_chapter_list').options[i] = new Option(chapter_list[i][0], chapter_list[i][1]);
}
document.getElementById('top_chapter_list').value=current_chapter;
document.getElementById('bottom_chapter_list').value=current_chapter;
var current_chapter_index = document.getElementById('top_chapter_list').selectedIndex;