Compilare: user.cpp: In function ‘int main()’: user.cpp:12:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<a.size();i++) ^ user.cpp:6:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("text.in","r",stdin); ^ user.cpp:7:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("text.out","w",stdout); ^