var mapImg = document.getElementById("fla");
var imgArray = ["images/pic_theater_on_a.gif","images/pic_theater_on_b.gif","images/pic_theater_on_c.gif","images/pic_theater.gif"]
function chImg (i) {
	var alertDiv = document.getElementById("map"+i);
	mapImg.src = imgArray[i-1]
	alertDiv.style.display = "block";
	}
function backImg (i){
	var alertDiv = document.getElementById("map"+i);
	mapImg.src = imgArray[imgArray.length-1];
	alertDiv.style.display = "none";
	}