Compilare: user.cpp: In function ‘void prime_num()’: user.cpp:22:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (nr <= DIM) ^ user.cpp:33:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (nr <= DIM) ^ user.cpp:48:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (nr <= DIM) ^ user.cpp: In function ‘int main()’: user.cpp:84:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ubercool.in","r",stdin); ^ user.cpp:85:43: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ubercool.out","w",stdout); ^ user.cpp:87:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:94:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld", &X); ^