Compilare: user.cpp: In function ‘void init(const std::string&)’: user.cpp:12: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:13: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘bool isPrime(std::vector<int, std::allocator<int> >&, const int&)’: user.cpp:19: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void test(std::vector<int, std::allocator<int> >&)’: user.cpp:29: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:42: warning: comparison between signed and unsigned integer expressions