var place = 0
var total = nav.length;

function setPos(p) {
  place = p;
}

function placement(inc) {
	if (inc == "add") {
		if ((place + 1) >= total) {
			return 0;
		}
		else {
			return (place + 1);
		}
	}
	else if (inc == "sub") {
		if ((place - 1) < 0) {
			return (total - 1);
		}
		else {
			return (place - 1);
		}
	}
}