function showTopic(t) {
  var topic = 'topic'+t;
  var disp = document.getElementById(topic).style.display;
  document.getElementById(topic).style.display = (disp=='none') ? 'block' : 'none';
}
function showAnswer(a) {
  var answer = 'ans'+a;
  var disp = document.getElementById(answer).style.display;
  document.getElementById(answer).style.display = (disp=='none') ? 'block' : 'none';
}
function showRelated(t, a) {
  var topic = 'topic'+t;
  var answer = 'ans'+a;
  document.getElementById(topic).style.display = 'block';
  document.getElementById(answer).style.display = 'block';
}
function closeAll() {
  var topic;
  for (t=1; t<=MAX_T; t++) {
    topic = 'topic'+t;
    document.getElementById(topic).style.display = 'none';
  }
  var answer;
  for (a=1; a<=MAX_A; a++) {
    answer = 'ans'+a;
    document.getElementById(answer).style.display = 'none';
  }
}
function getQ() {
  if (window.location.hash != "") {
    var wlh = window.location.hash;
    var t = wlh.substring(wlh.indexOf("T")+1, wlh.indexOf("Q"));
    var q = wlh.substring(wlh.indexOf("Q")+1, wlh.length);
      if (t>0 && t<=MAX_T && q>0 && q<MAX_A) {
        showRelated(t,q);
        window.location.hash = "q"+q;
      }
  }
}