function chgBar (i,b,c)
{
  var button, content;
  if (i % 2 == 0)
  {
    button = b[1];
    content = c[1];
  }
  else
  {
    button = b[0];
    content = c[0];
  }
  document.getElementById('bar_button').innerHTML = button;
  document.getElementById('bar_content').innerHTML = content;
  i++;
  return i;
}