Compilare: user.cpp: In function 'int main()': user.cpp:70: warning: comparison between signed and unsigned integer expressions user.cpp:83: warning: comparison between signed and unsigned integer expressions user.cpp:85: warning: comparison between signed and unsigned integer expressions user.cpp:101: warning: comparison between signed and unsigned integer expressions user.cpp:103: warning: comparison between signed and unsigned integer expressions user.cpp:109: warning: comparison between signed and unsigned integer expressions user.cpp:128: warning: comparison between signed and unsigned integer expressions