Compilare: user.cpp: In function ‘int main()’: user.cpp:56:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(x = 1; x <= vx.size(); ++x) ^ user.cpp:57:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(y = 1; y <= vy.size(); ++y) ^ user.cpp:73:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(z = 1; z <= vz.size(); ++z) ^