Compilare: user.cpp: In function ‘int main()’: user.cpp:13: warning: comparison between signed and unsigned integer expressions user.cpp:14: warning: comparison between signed and unsigned integer expressions user.cpp:25: warning: comparison between signed and unsigned integer expressions user.cpp:26: warning: comparison between signed and unsigned integer expressions user.cpp:29: warning: comparison between signed and unsigned integer expressions user.cpp:30: warning: comparison between signed and unsigned integer expressions