function changesign(){
	var x="80";
	var y="80";
	var z="70";
	while (y == x){
	x=Math.floor(Math.random()*83);
	y=Math.floor(Math.random()*86);
	z=Math.floor(Math.random()*71);
	}
	var newsign=("  "+a[x]+" "+b[y]+" "+c[z]+"  ");
	document.getElementById('para').innerHTML = newsign;}