function pic_roll() {
	this.name = "pic";
	this.cur_idx = 1;
	this.last_idx;
	this.show_idx = 1;
	this.show_sec = 5;
	this.chk_cnt = 0;
	this.auto_flow = function(){
		//alert(this.chk_cnt);
		if(this.chk_cnt + 1 == this.show_sec) {
			this.chk_cnt = 1;
			this.next_pic();
		}
		else {
			this.chk_cnt++;
		}
		window.setTimeout(this.name + ".auto_flow();", 1000);
	}
	this.next_pic = function () {
		if(this.cur_idx == this.last_idx) {
			this.cur_idx = 1;
		}
		else {
			this.cur_idx++;
		}
		this.show_pic(this.cur_idx);
	}
	this.prev_pic = function () {
		if(this.cur_idx == 1) {
			this.cur_idx = this.last_idx;
		}
		else {
			this.cur_idx--;
		}
		this.show_pic(this.cur_idx);
	}
	this.show_pic = function (idx) {
		var show_id = this.name + this.show_idx;
		show_obj = document.getElementById(show_id);
		show_obj.style.display = "none";
		var div_id  = this.name + idx;
		this.show_idx = idx;
		new_obj = document.getElementById(div_id);
		new_obj.style.display = "";
		this.chk_cnt = 1;
	}
}