text: #include<iostream>
  #include<vector>
  
  
  using namespace std;
  
  class Solution {
  public:
      int xorOperation(int n, int start) {
          int res = start + 2 * 0;
          for (int i(1); i < n; i++)
              res ^= start + 2 * i;
          return res;
      }
  };
  
  int main() {
      Solution solution;
      cout << solution.xorOperation(10, 5) << endl;
      return 0;
  }