Compilare: user.cpp: In function ‘char Advance()’: user.cpp:22:38: 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, stdin); ^ user.cpp: In function ‘int main()’: user.cpp:56:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sieve.in", "r", stdin); ^ user.cpp:57:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sieve.out", "w", stdout); ^