Compilare: user.cpp: In function ‘int main()’: user.cpp:10: warning: unused variable ‘M’ user.cpp:10: warning: unused variable ‘j’ user.cpp:11: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result 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 ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result