var stack;
//var NUM_ELEMENTS = 10
var NUM_ELEMENTS = 8;

function shift_stack() {
	for(i = 0; i < stack.length; i++) {
		id = stack[i];
		var el = document.getElementById("item" + String(id))
		el.className = i < NUM_ELEMENTS ? "p" + String(i) : "hidden";

	}	
	stack.push(stack.shift())
}



function init_stack(interval, time) {
	stack = new Array();
	
	var i = 0;
	while(true) {
		if(document.getElementById( "item" + String(i) )) {
			i++;
		} else
			break;
	}
	var n = i;
	
	var k = Math.round(time / interval) % n;
	
	for(var i = k; i < n; i++)
		stack.push(i);
	for(var i = 0; i < k; i++)
		stack.push(i);

	shift_stack();
	
	var aktiv = window.setInterval("shift_stack()", interval * 1000);
}