Eroare de compilare: user.cpp: In function ‘std::vector<int, std::allocator<int> > prefix(const std::string&)’: user.cpp:18: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:32: error: ‘stdin’ was not declared in this scope user.cpp:32: error: ‘freopen’ was not declared in this scope user.cpp:33: error: ‘stdout’ was not declared in this scope