Compilare: user.cpp: In function ‘int main()’: user.cpp:123:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0; j<M.size(); j++) ^ user.cpp: In member function ‘char InParser::read_ch()’: user.cpp:20:38: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buff, 1, 4096, fin); ^