Compilare: user.cpp: In function 'int main()': user.cpp:85: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void DF_out(int)': user.cpp:104: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void DF_in(int)': user.cpp:118: warning: comparison between signed and unsigned integer expressions user.cpp:132: warning: comparison between signed and unsigned integer expressions