Compilare: user.cpp: In function ‘int main()’: user.cpp:27:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<v[i].size(); ++j) ^ user.cpp:29:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<v[i].size(); ++j) ^ user.cpp:33:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0; k<v[x].size(); ++k) ^ user.cpp:37:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<v[i].size(); ++j) ^