Compilare: user.cpp: In function ‘void mul(long long unsigned int*, long long unsigned int)’: user.cpp:16: warning: comparison between signed and unsigned integer expressions user.cpp:18: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:50: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:51: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result