View Compilation Error

0_0_19722771_24717.cpp: In function 'void Solve()':
0_0_19722771_24717.cpp:99:18: error: 'roots' was not declared in this scope
         if( tree[roots].sum < K ) K = tree[roots].sum;
                  ^
0_0_19722771_24717.cpp:100:22: error: 'roots' was not declared in this scope
         ans += query(roots,K);
                      ^