Compilare: user.cpp: In function ‘bool exista(int)’: user.cpp:18:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[m].size(); ++i) ^ user.cpp: In function ‘void del(int)’: user.cpp:33:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[m].size(); ++i) ^