std::vector<char> add11(const std::vector<char>& left, const std::vector<char>& right){
    std::vector<char> result;
    result.resize(left.size()>right.size()?left.size():right.size());
    int carry = 0;
    for(size_t i = 0;i<result.size();i++){
        int carry = int(left[i]) + int(right[i])+ carry;
        if(carry > 11){
            carry-=11;
        }

        result[i] = char(carry);
        if(result[i] == '11'){
            result[i] = 'A';
        }

    }
    return result;
}