Compilare: user.cpp: In function ‘int main()’: user.cpp:21:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= N; ++i) ^ user.cpp:26:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= N; ++i) ^ user.cpp:55:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= N; ++i) ^