/*
    Search for the Kth Ancestor of a Tree Node
*/
#include <vector>
#include <bit>
#include <bitset>
#include <cstdint>

class TreeAncestor {
private:
    std::vector<std::vector<int>> predecessor;

public:
    TreeAncestor(int n, std::vector<int>& parent) {
        int m = bit_width((unsigned)n);
        predecessor.resize(n, std::vector<int>(m, -1));
        for (int i = 0; i < n; i++) {
            predecessor[i][0] = parent[i];
        }
        for (int i = 1; i < m; i++) {
            for (int x = 0; x < n; x++) {
                if (int p = predecessor[x][i - 1]; p != -1) {
                    predecessor[x][i] = predecessor[p][i - 1];
                }
            }
        }
    }

    int getKthAncestor(int node, int k) {
        // for (int i = 0; i < bit_width((unsigned)k) && node != -1; i++) {
        //    if (k >> i & 1) {
        //        node = predecessor[node][i];
        //    }
        // }
        for (; k && node != -1; k &= k - 1) {
            node = predecessor[node][countr_zero(unsigned(k))];
        }
        return node;
    }
};