Compilare: user.cpp: In function ‘long long int dfs2(long long int, long long int)’: user.cpp:77:15: warning: unused variable ‘answer’ [-Wunused-variable] long long answer = 0; ^ user.cpp: In member function ‘void input_reader::advance()’: user.cpp:18:49: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^ user.cpp: In constructor ‘input_reader::input_reader(const char*)’: user.cpp:28:45: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread( buffer, SIZE, 1, input_file ); ^