var j = 2;
var k = 1;
var l = 1;
var n = 1;
var m = 1;
var o = 1;
function fchange1() {
	var nav_img1 = document.getElementById("nav_img1");
	var nav_box1 = document.getElementById("nav_box1");
	if ( j == 1 ) {
			nav_img1.src = "letsgo_images/title/course_title_1_r.gif";
			nav_box1.style.display = "block";
			j = 2;
			}
			else {
				nav_img1.src = "letsgo_images/title/course_title_1.gif";
				nav_box1.style.display = "none";
				j = 1;
				}
	}
function fchange2() {
	var nav_img2 = document.getElementById("nav_img2");
	var nav_box2 = document.getElementById("nav_box2");
	if ( k == 1 ) {
			nav_img2.src = "letsgo_images/title/course_title_2_r.gif";
			nav_box2.style.display = "block";
			k = 2;
			}
			else {
				nav_img2.src = "letsgo_images/title/course_title_2.gif";
				nav_box2.style.display = "none";
				k = 1;
				}
	}

function fchange3() {
	var nav_img3 = document.getElementById("nav_img3");
	var nav_box3 = document.getElementById("nav_box3");
	if ( l == 1 ) {
			nav_img3.src = "letsgo_images/title/course_title_3_r.gif";
			nav_box3.style.display = "block";
			l = 2;
			}
			else {
				nav_img3.src = "letsgo_images/title/course_title_3.gif";
				nav_box3.style.display = "none";
				l = 1;
				}
	}

function fchange4() {
	var nav_img4 = document.getElementById("nav_img4");
	var nav_box4 = document.getElementById("nav_box4");
	if ( n == 1 ) {
			nav_img4.src = "letsgo_images/title/course_title_4_r.gif";
			nav_box4.style.display = "block";
			n = 2;
			}
			else {
				nav_img4.src = "letsgo_images/title/course_title_4.gif";
				nav_box4.style.display = "none";
				n = 1;
				}
	}
	
function fchange5() {
	var nav_img5 = document.getElementById("nav_img5");
	var nav_box5 = document.getElementById("nav_box5");
	if ( m == 1 ) {
			nav_img5.src = "letsgo_images/title/course_title_5_r.gif";
			nav_box5.style.display = "block";
			m = 2;
			}
			else {
				nav_img5.src = "letsgo_images/title/course_title_5.gif"
				nav_box5.style.display = "none";
				m = 1;
				}
	}
	
function fchange6() {
	var nav_img6 = document.getElementById("nav_img6");
	var nav_box6 = document.getElementById("nav_box6");
	if ( o == 1 ) {
			nav_img6.src = "letsgo_images/title/course_title_6_r.gif"
			nav_box6.style.display = "block";
			o = 2;
			}
			else {
				nav_img6.src = "letsgo_images/title/course_title_6.gif"
				nav_box6.style.display = "none";
				o = 1;
				}
	}
	
function nav_fn(ac) {
	for (i=1;i<20;i++){
		var dd = document.getElementById("sub_nav"+i);
		var tt = document.getElementById("sub_nav_box"+i);
		if (ac=="ac"+i) {
			if ( tt.style.display=="block") {
				tt.style.display = "none";
				}
				
			else if ( tt.style.display == "none"){
				tt.style.display="block";		
				}
			}
		}
	}