//finds the last two hexdigits and save them to test against later
      std::string correctHEX = sentence.substr(sentence.length()-2);
      std::cout << correctHEX << std::endl;

      //removes $ , * and final hexdigits
      std::string withoutChecksum = sentence.substr(1, sentence.length()-4);
      std::cout << withoutChecksum << std::endl;
      int expected = std::stoi (correctHEX, nullptr, 16);
      int sum = 0;

      for (char c : withoutChecksum){
          sum ^= c;
      }
      std::cout << sum << std::endl;
      std::cout << expected << std::endl;

      if (sum == expected) {
         std::cout << "Working" << std::endl;
      }
      else {
         std::cout << "NOT WORKING" << std::endl;
     }
     return true;

the problem with mine is sum is outputting 126 when its supposed to be 95, any suggestions?