Compilare: user.cpp: In function ‘void df(int)’: user.cpp:15: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void df2(int)’: user.cpp:28: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:53: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:54: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:55: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:60: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result