Eroare de compilare: user.cpp: In function ‘int valid(int)’: user.cpp:17: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void back(int)’: user.cpp:28: warning: comparison between signed and unsigned integer expressions user.cpp:47: warning: suggest explicit braces to avoid ambiguous ‘else’ user.cpp:55: warning: comparison between signed and unsigned integer expressions user.cpp:55: warning: suggest explicit braces to avoid ambiguous ‘else’ user.cpp: In function ‘int main()’: user.cpp:73: error: ‘nr’ was not declared in this scope