Compilare: user.cpp: In function ‘int main()’: user.cpp:52: warning: comparison between signed and unsigned integer expressions user.cpp:54: warning: comparison between signed and unsigned integer expressions user.cpp:57: warning: comparison between signed and unsigned integer expressions user.cpp:58: warning: comparison between signed and unsigned integer expressions user.cpp:59: warning: comparison between signed and unsigned integer expressions user.cpp:62: warning: comparison between signed and unsigned integer expressions