Compilare: user.cpp: In function 'void df(int, bool)': user.cpp:28: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'int main()': user.cpp:86: warning: comparison between signed and unsigned integer expressions user.cpp:98: warning: comparison between signed and unsigned integer expressions user.cpp:101: warning: comparison between signed and unsigned integer expressions user.cpp:104: warning: comparison between signed and unsigned integer expressions