Compilare: user.cpp: In function ‘unsigned int sieve(unsigned int)’: user.cpp:12:67: warning: unused variable ‘jIndex’ [-Wunused-variable] register unsigned i, j, iBitNumber, iIndex, iBit, jBitNumber, jIndex, jBit, count = 2; ^~~~~~ user.cpp:12:75: warning: unused variable ‘jBit’ [-Wunused-variable] register unsigned i, j, iBitNumber, iIndex, iBit, jBitNumber, jIndex, jBit, count = 2; ^~~~ user.cpp: In function ‘int main()’: user.cpp:69:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ciur.in", "r", stdin); ^ user.cpp:70:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ciur.out", "w", stdout); ^ user.cpp:72:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] unsigned N; scanf("%u", &N); ^