View Compilation Error

0_0_34487507_26737.cpp: In function 'int main()':
0_0_34487507_26737.cpp:69:63: error: 'std::vector<long long int>::iterator' has no member named 'size'
           ll si =  Y.erase(unique(Y.begin(),Y.end()),Y.end()).size();
                                                               ^