Compilare: user.cpp: In function ‘int main()’: user.cpp:32: warning: comparison between signed and unsigned integer expressions user.cpp:33: warning: operation on ‘j’ may be undefined 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