Compilare: user.cpp: In function 'int main()': user.cpp:20: warning: comparison between signed and unsigned integer expressions user.cpp:22: warning: comparison between signed and unsigned integer expressions user.cpp:24: warning: comparison between signed and unsigned integer expressions user.cpp:30: warning: comparison between signed and unsigned integer expressions user.cpp:32: warning: comparison between signed and unsigned integer expressions user.cpp:34: warning: comparison between signed and unsigned integer expressions user.cpp:40: warning: comparison between signed and unsigned integer expressions user.cpp:42: warning: comparison between signed and unsigned integer expressions user.cpp:44: warning: comparison between signed and unsigned integer expressions