var chapter_list = new Array(
  ["Vol.01 Ch.001: Ogre's Choise","v01/c001"],
  ["Vol.01 Ch.002: The Second Choise","v01/c002"],
  ["Vol.01 Ch.003: Ogress","v01/c003"],
  ["Vol.01 Ch.004: Tactics","v01/c004"],
  ["Vol.01 Ch.005: Vulnerability","v01/c005"],
  ["Vol.01 Ch.006: Contact","v01/c006"],
  ["Vol.01 Ch.007: The Black","v01/c007"],
  ["Vol.01 Ch.008: Transfer","v01/c008"],
  ["Vol.01 Ch.009: Revitalization","v01/c009"],
  ["Vol.01 Ch.010.1: Destruction","v01/c010.1"],
  ["Vol.01 Ch.010.2: Destruction","v01/c010.2"]
);

var total_chapters = 11;

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;