Subtree Add, Point Get

**Bài toán.** A rooted tree (root 1), parents for v = 2..n, all initial values 0. q operations: SA v x adds x to every node of subtree(v); GET v prints the current value of node v. **Constraints:** 1 ≤ n, q ≤ 200 000; |x| ≤ 10^9; answers fit in long long. Euler tour + difference BIT: O(log n) per operation.