Compilare: main.cpp: In function 'int main()': main.cpp:203:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(ans.size() == n) ~~~~~~~~~~~^~~~ main.cpp:207:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < ans.size(); ++i) ~~^~~~~~~~~~~~ main.cpp: In member function 'char InParser::read_ch()': main.cpp:28:29: 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); ^