Compilare: user.cpp: In function 'void df(int)': user.cpp:29: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'int main()': user.cpp:89: warning: comparison between signed and unsigned integer expressions user.cpp:102: warning: comparison between signed and unsigned integer expressions user.cpp:105: warning: comparison between signed and unsigned integer expressions user.cpp:108: warning: comparison between signed and unsigned integer expressions