function init() {
  var container = document.getElementById("captcha-widget-main");
  if (!container) return;
  var observer = new MutationObserver(function(mutations) {
    mutations.forEach(function(mutation) {
      Array.prototype.filter.call(mutation.addedNodes, function(node) {
        return node.tagName === "IMG";
      }).forEach(function(){ans();});
    });
  });
  observer.observe(container, {childList: true});
}