Eroare de compilare: user.cpp: In function ‘int mai()’: user.cpp:16: error: ‘struct std::pair<int, int>’ has no member named ‘push_back’ user.cpp:27: error: ‘struct std::pair<int, int>’ has no member named ‘size’ user.cpp:29: error: no match for ‘operator[]’ in ‘a.std::vector<_Tp, _Alloc>::operator[] [with _Tp = std::pair<int, int>, _Alloc = std::allocator<std::pair<int, int> >](((unsigned int)k))[i]’ user.cpp:30: error: no match for ‘operator[]’ in ‘a.std::vector<_Tp, _Alloc>::operator[] [with _Tp = std::pair<int, int>, _Alloc = std::allocator<std::pair<int, int> >](((unsigned int)k))[i]’