Compilare: user.cpp: In function ‘int main()’: user.cpp:28:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<L[x].size(); ++i) ^ user.cpp:45:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<L[x].size(); ++i) ^ user.cpp:62:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<L[x].size(); ++i) ^