Compilare: user.cpp: In function ‘void read()’: user.cpp:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘void df1(int)’: user.cpp:48: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void df2(int, int)’: user.cpp:60: warning: comparison between signed and unsigned integer expressions