16de34c9-edb2-4549-b598-8418b95e578d
16de34c9-edb2-4549-b598-8418b95e578d(47): error: no operator ">>" matches these operands
            operand types are: std::istream >> std::string
          cin>>tmp;
             ^

16de34c9-edb2-4549-b598-8418b95e578d(48): error: no operator "==" matches these operands
            operand types are: std::string == char [3]
          if (tmp=="-1")
                 ^

16de34c9-edb2-4549-b598-8418b95e578d(57): error: no operator ">>" matches these operands
            operand types are: std::istream >> std::string
              cin>>temp_word;
                 ^

16de34c9-edb2-4549-b598-8418b95e578d(74): error: no operator "==" matches these operands
            operand types are: std::string == char [1]
          if (books[i].otvet=="")
                            ^

16de34c9-edb2-4549-b598-8418b95e578d(77): error: no operator "<<" matches these operands
            operand types are: std::ostream << std::string
              cout<<books[i].otvet<<endl;
                  ^

compilation aborted for 16de34c9-edb2-4549-b598-8418b95e578d (code 2)
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But on my Unix system (g++) there are no errors.
I don't know what does it mean(