View Compilation Error

0_0_37690204_2583.cpp: In function 'void build(int, int, int)':
0_0_37690204_2583.cpp:24:11: error: 'lc' was not declared in this scope
     build(lc, l, mid);
           ^
0_0_37690204_2583.cpp: In function 'void update(int, int)':
0_0_37690204_2583.cpp:36:16: error: 'lc' was not declared in this scope
         update(lc, k);
                ^
0_0_37690204_2583.cpp:39:24: error: 'lc' was not declared in this scope
     tree[p].num = tree[lc].num + tree[rc].num;
                        ^
0_0_37690204_2583.cpp: In function 'int query(int, int, int)':
0_0_37690204_2583.cpp:52:26: error: 'lc' was not declared in this scope
             sum += query(lc, k, n);
                          ^