function cool(num){
 for(i=0;i<5;i++){
  if(i==num){
   document.getElementById("content"+i).className="shw"; 
   }
  else{
  document.getElementById("content"+i).className="dis";
  }
 }
}
function cool2(){
   document.getElementById("content0").className="shw"; 
   document.getElementById("content1").className="dis";
   document.getElementById("content2").className="dis";
   document.getElementById("content3").className="dis";
   document.getElementById("content4").className="dis";
}