Compilare: user.cpp: In function ‘int main()’: user.cpp:62:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < elements.size(); ++ i) ^ user.cpp:24:26: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(FIN, "r", stdin); ^ user.cpp:25:28: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(FOUT, "w", stdout); ^