[LintCode] 第一个错误的代码版本

 /**
  * class VersionControl {
  *     public:
  *     static bool isBadVersion(int k);
  * }
  * you can use VersionControl::isBadVersion(k) to judge whether
  * the kth code version is bad or not.
 */
 class Solution {
 public:
     /**
      * @param n: An integers.
      * @return: An integer which is the first bad version.
      */
     int findFirstBadVersion(int n) {
         // write your code here
         int l = , r = n;
         while (l < r) {
             int m = (l + r) / ;
             if (VersionControl::isBadVersion(m)) r = m;
             else l = m + ;
         }
         return l;
     }
 };