function setchap(index, s1) {
  var i,j,k,txt;
  var cnum=new Array(50,40,27,36,34,24,21,4,31,24,22,25,29,36,10,13,10,42,150,31,12,8,66,52,5,48,12,14,3,9,1,4,7,3,3,3,2,14,4, 28,16,24,21,28,16,16,13,6,6,4,4,5,3,6,4,3,1,13,5,5,3,5,1,1,1,22);
  i=cnum[index];

  var objchapter = document.getElementById("chapter");

  var currentchapters = objchapter.options.length;
  
  if((i == 150) && (currentchapters < 150))
    for(j = 1; j <= 150;j++) {
      txt = "第 " + j + " 篇";
      objchapter.options[j-1] = new Option(txt, j);  
    }
  else if((i < 150) && (currentchapters == 150)) {
    for(j = 1; j <= i; j++) {
      txt = "第 " + j + " 章";
      objchapter.options[j-1] = new Option(txt, j);
    }
    for(j = 150;j > i;j=j-1)
      objchapter.options[j-1] = null;
  }
  else if (i > currentchapters)
    for(j = currentchapters; j <= i; j++) {
      txt = "第 " + j + " 章";
      objchapter.options[j-1] = new Option(txt, j);
    }
  else if (i < currentchapters)
    for(j = currentchapters; j > i; j=j-1)
      objchapter.options[j-1] = null;


  objchapter.options[0].selected = s1;

}