class Solution {

 public:

     string printRange(int lower, int upper) {

         string low = std::to_string(lower);

         string up = std::to_string(upper);

         if (lower == upper) return low;

         return low + "->" + up;

     }

     vector<string> findMissingRanges(vector<int>& nums, int lower, int upper) {

         vector<string> res;

         if (nums.size() == ) res.push_back(printRange(lower, upper));

         else if (nums.front() > lower) res.push_back(printRange(lower, nums.front() - ));

         for (int i = , n = nums.size(); i < n; i++)

             if (nums[i] > nums[i-] + )

                 res.push_back(printRange(nums[i-] + , nums[i] - ));

         if (nums.size() >  && nums.back() < upper)

             res.push_back(printRange(nums.back() + , upper));

         return res;

     }

 };