Compilare: user.cpp: In function ‘int main()’: user.cpp:18: warning: operation on ‘k’ may be undefined user.cpp:20: warning: operation on ‘k’ may be undefined user.cpp:7: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:8: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result