Compilare: user.cpp: In function ‘int main()’: user.cpp:29:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[k].v.size();i++) ^ user.cpp:42:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[k].v.size();i++) ^