Compilare: user.cpp: In function ‘int main()’: user.cpp:38:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<v[m].size();++j) if (v[m][j].first==x) {++v[m][j].second;break;} ^ user.cpp:39:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (j>=v[m].size()) ^ user.cpp:46:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<v[i].size();++j) ^