Compilare: user.cpp: In function ‘int main()’: user.cpp:45: warning: comparison between signed and unsigned integer expressions user.cpp:50: warning: comparison between signed and unsigned integer expressions user.cpp:24: warning: unused variable ‘i’ user.cpp:24: warning: unused variable ‘j’ user.cpp:24: warning: unused variable ‘k’ user.cpp:25: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:26: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result