function  test(){

var txt = confirm("Are you sure?");

if(txt){
  return true;
}else{
  return false;
}

}
 function swap(thatpic,thispic){

  var pic_1 = document.getElementById(thatpic).src;
  var pic_2 = document.getElementById(thispic).src;


  document.getElementById(thatpic).src = pic_2.replace('_s.jpg','.jpg');
//  document.getElementById(thispic).src = pic_1.replace('.jpg','_s.jpg');

}