Compilare: user.cpp: In function ‘bool is_prime(long long int)’: user.cpp:29: warning: suggest parentheses around comparison in operand of ‘&’ user.cpp: In function ‘int main()’: user.cpp:51: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:52: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:55: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:58: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result