function shownav(num){
var nav=3;
for (i=1; i<=nav; i++){
if (i==num){
document.getElementById("nav"+i+"s").style.display="";
document.getElementById("nav"+i).className="btn-on";
}else{
document.getElementById("nav"+i+"s").style.display="none";
document.getElementById("nav"+i).className="btn-off";
}
}
}