Compilare: user.cpp: In function ‘int main()’: user.cpp:22:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[1].size();++i) ^ user.cpp:29:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[2].size();++i) ^ user.cpp:37:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[0].size();++i) ^