add break

Highest and lowest/main.cpp

@@ -11,5 +11,5 @@ std::string highAndLow(const std::string& numbers){
     nums.push_back(num);
   }
   auto min_max = std::minmax_element(nums.begin(), nums.end());
-  return std::is_string(*min_max.second()) + " " +  std::string(*min_max.first();)
+  return is_string(*min_max.second) + " " +  is_string(*min_max.first);
 }