View Compilation Error

0_0_35679534_17491.cpp: In function 'void update(int, int, int, int, int)':
0_0_35679534_17491.cpp:19:19: error: 'z' was not declared in this scope
      tree[root] = z;
                   ^
0_0_35679534_17491.cpp:23:38: error: 'z' was not declared in this scope
     if(x<=mid) update(l,mid,root*2,x,z);
                                      ^
0_0_35679534_17491.cpp:24:36: error: 'z' was not declared in this scope
     else update(mid+1,r,root*2+1,x,z);
                                    ^