function check(n){
    for(var i=1;i<=3;i++){ 
	 var strA = document.getElementById("tn");
	 var strB = document.getElementById("tab"+i);
	if (n==i){
	  strA.className = "tab"+i;
	  strB.style.color="#fff";
	}else{ strB.style.color="#373737";}
	}
  }