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: Sidestory- It's Unintentional!","v01/c004"],
  ["Vol.01 Ch.005: Sidestory- Only","v01/c005"],
  ["Vol.02 Ch.001","v02/c001"],
  ["Vol.02 Ch.002","v02/c002"],
  ["Vol.02 Ch.003","v02/c003"],
  ["Vol.02 Ch.004: Sidestory - Prince of Summer","v02/c004"],
  ["Vol.02 Ch.005: Sidestory - You","v02/c005"],
  ["Vol.03 Ch.001: Summer of a Decisive Battle","v03/c001"],
  ["Vol.03 Ch.002: Final Answer?","v03/c002"],
  ["Vol.03 Ch.003: End- Love Coliseum","v03/c003"],
  ["Vol.03 Ch.004: Sidestory - The Mushroom Girl","v03/c004"]
);

var total_chapters = 14;

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;