Compilare: user.cpp: In function ‘int main()’: user.cpp:43:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1 ; i < s.size() ; ++ i) { ^ user.cpp:33:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(infile, "r", stdin); ^ user.cpp:34:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(outfile, "w", stdout); ^