$(document).ready(function() {

$("#nav ul").hide();
$("#nav li:has(ul)").each(function() {
$(this).children().slideUp(400);
});

$("li.p1:has(ul)").click(function(event){
if (this == event.target) {
var current = this;
$("#nav li:has(ul)").each(function() {
if (this != current) $(this).children().slideUp(400);
});
$("ul:first", $(this)).slideToggle(400);
}
});

$("li.p2:has(ul)").click(function(event){
if (this == event.target) {
var current = this;
$("li.p2:has(ul)").each(function() {
if (this != current) $(this).children().slideUp(400);
});
$("li.p3:has(ul)").each(function() {
if (this != current) $(this).children().slideUp(400);
});
$("ul:first", $(this)).slideToggle(400);
}
});

$("li.p3:has(ul)").click(function(event){
if (this == event.target) {
var current = this;
$("li.p3:has(ul)").each(function() {
if (this != current) $(this).children().slideUp(400);
});
$("ul:first", $(this)).slideToggle(400);
}
});

});