View Compilation Error

0_0_13156144_14194.cpp:15:7: error: 'maxn' was not declared in this scope
 }tree[maxn*4];
       ^
0_0_13156144_14194.cpp: In function 'void btree(int, int, int)':
0_0_13156144_14194.cpp:18:5: error: 'tree' was not declared in this scope
     tree[rt].left=left;
     ^
0_0_13156144_14194.cpp: In function 'void query(int, int, int, int, int)':
0_0_13156144_14194.cpp:34:14: error: 'tree' was not declared in this scope
         ans+=tree[rt].sum;
              ^
0_0_13156144_14194.cpp:37:13: error: 'tree' was not declared in this scope
     int mid=tree[rt].mid();
             ^
0_0_13156144_14194.cpp: In function 'void update(int, int, int, int, int)':
0_0_13156144_14194.cpp:50:3: error: 'tree' was not declared in this scope
   tree[rt].sum += add;
   ^
0_0_13156144_14194.cpp:53:12: error: 'tree' was not declared in this scope
  int mid = tree[rt].mid();
            ^