Compilare: user.cpp: In function ‘int main()’: user.cpp:133:8: warning: unused variable ‘_’ [-Wunused-variable] bool _ = check (sol); ^ user.cpp: In function ‘char advance()’: user.cpp:13:32: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, 1, SIZE, fin); ^