<!DOCTYPE HTML>
<html>
<head>
<script>
function show_alert()
{
www.value=qqq.value*[[1,3],[2,4]][+G1.checked][+G2.checked];
}
</script>
</head><body>
<input id="qqq">
<input type="checkbox" id="G1"> <input type="checkbox" id="G2">
<input type="button" value="Go! " onclick="show_alert()">
<br>
<input id="www">
</body>
</html>