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<script>
var modal= document.getElementById('modal');
var shade= document.getElementById('shade');
document.getElementById('start').onclick= function() {
modal.style.display=shade.style.display= 'block';
};
document.getElementById('close').onclick= function() {
modal.style.display=shade.style.display= 'none';
};
if (!('maxHeight' in document.body.style)) {
function modalsize() {
var top= document.documentElement.scrollTop;
var winsize= document.documentElement.offsetHeight;
var docsize= document.documentElement.scrollHeight;
shade.style.height= Math.max(winsize, docsize)+'px';
modal.style.top= top+Math.floor(winsize/3)+'px';
};
modal.style.position=shade.style.position= 'absolute';
window.window.modalsize;
modalsize();
}
</script>