Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:62: error: no match for ‘operator+=’ in ‘s += ((i < K) ? big_number<1000000000>(((const big_number<1000000000>&)((const big_number<1000000000>*)D.std::vector<_Tp, _Alloc>::operator[] [with _Tp = big_number<1000000000>, _Alloc = std::allocator<big_number<1000000000> >](((unsigned int)i))))) : big_number<base>::operator-(big_number<base>&) const [with int base = 1000000000](((big_number<1000000000>&)((big_number<1000000000>*)D.std::vector<_Tp, _Alloc>::operator[] [with _Tp = big_number<1000000000>, _Alloc = std::allocator<big_number<1000000000> >](((unsigned int)(i - K)))))))’ user.cpp:22: note: candidates are: big_number<base>& big_number<base>::operator+=(big_number<base>&) [with int base = 1000000000] user.cpp: In member function ‘big_number<base> big_number<base>::operator-(big_number<base>&) const [with int base = 1000000000]’: user.cpp:62: instantiated from here user.cpp:17: warning: comparison between signed and unsigned integer expressions user.cpp:62: instantiated from here user.cpp:18: warning: comparison between signed and unsigned integer expressions