View Compilation Error

0_0_26499001_9965.cpp: In function 'node* build(ll, ll, bool)':
0_0_26499001_9965.cpp:53:57: error: 'nth_element' was not declared in this scope
         nth_element(stk+l,stk+mid,stk+r+1,!f?cmp_x:cmp_y);
                                                         ^
0_0_26499001_9965.cpp: In function 'void solve()':
0_0_26499001_9965.cpp:157:34: error: 'sort' was not declared in this scope
     sort(points+1,points+1+n,cmpk);
                                  ^