var bpht1 = new Array();
var bpht2 = new Array();
for(var i=1;i<=4;i++){
	bpht1[i] = new Image();
	bpht1[i].src = "./img/c" + i + ".png";
	bpht2[i] = new Image();
	bpht2[i].src = "./img/cb" + i + ".png";
}
function bChg1(nb){
	var mtd = "mb" + nb;
	document.getElementById(mtd).src = bpht1[nb].src;
}
function bChg2(nb){
	var mtd = "mb" + nb;
	document.getElementById(mtd).src = bpht2[nb].src;
}