View Compilation Error

0_0_30021272_27834.cpp: In function 'bool check(int, int, int, int, int, int)':
0_0_30021272_27834.cpp:72:51: error: 'query' was not declared in this scope
  ll res = query(root[ql - 1], root[qr], L, R, 1, n);
                                                   ^