var yiimgk = new Array;
var yiufnk = new Array;
var yisfnk = new Array;

function yiadd(i,fn) {
  yiimgk[i]=new Image; yiimgk[i].src=fn;
  yiufnk[i]=null; yisfnk[i]=fn;
}

function yisel(i) {
  if (yiufnk[i]==null) yiufnk[i]=document.images[i].src;
  document.images[i].src=yisfnk[i];
}

function yiusel(i) {
  if (yiufnk[i]==null) yiufnk[i]=document.images[i].src;
  document.images[i].src=yiufnk[i];
}