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.005","v01/c005"],
  ["Vol.01 Ch.006","v01/c006"],
  ["Vol.01 Ch.007","v01/c007"],
  ["Vol.01 Ch.008","v01/c008"],
  ["Vol.01 Ch.009","v01/c009"],
  ["Vol.02 Ch.010","v02/c010"],
  ["Vol.02 Ch.011","v02/c011"],
  ["Vol.02 Ch.012","v02/c012"],
  ["Vol.02 Ch.013","v02/c013"],
  ["Vol.02 Ch.014","v02/c014"],
  ["Vol.02 Ch.015","v02/c015"],
  ["Vol.02 Ch.016","v02/c016"],
  ["Vol.02 Ch.017","v02/c017"],
  ["Vol.02 Ch.018","v02/c018"],
  ["Vol.02 Ch.019","v02/c019"],
  ["Vol.03 Ch.000","v03/c000"],
  ["Vol.04 Ch.000","v04/c000"],
  ["Vol.05 Ch.000","v05/c000"],
  ["Vol.06 Ch.000","v06/c000"],
  ["Vol.07 Ch.000","v07/c000"],
  ["Vol.08 Ch.000","v08/c000"],
  ["Vol.09 Ch.000","v09/c000"],
  ["Vol.10 Ch.000","v10/c000"],
  ["Vol.11 Ch.001","v11/c001"],
  ["Vol.11 Ch.002","v11/c002"],
  ["Vol.11 Ch.003","v11/c003"],
  ["Vol.11 Ch.004","v11/c004"],
  ["Vol.11 Ch.005","v11/c005"],
  ["Vol.11 Ch.006","v11/c006"],
  ["Vol.11 Ch.007","v11/c007"],
  ["Vol.11 Ch.008","v11/c008"],
  ["Vol.11 Ch.009","v11/c009"],
  ["Vol.11 Ch.010","v11/c010"]
);

var total_chapters = 37;

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;