Shared code

#include <iostream>
#include <vector>

using ll = long long;

int const nmax = 200000;
int parent[1 + nmax];
int far[1 + nmax];
int level[1 + nmax];

int main() {
  int n, q;
  std::cin >> n >> q;
  for(int i = 2; i <= n; i++)
    std::cin >> parent[i];
  level[1] = 1;
  for(int i = 2; i <= n; i++) {
    level[i] = level[parent[i]] + 1;
    int father = parent[i];
    int father2 = far[father];
    if(far[father2] != 0 && level[father] - level[father2] == level[father2] - level[far[father2]]) {
      far[i] = far[father2];
    } else
      far[i] = father;
  }

  for(int i = 1;i <= q; i++) {
    int node, k;
    std::cin >> node >> k;
    while(0 < k && 0 < node) {
      if(level[node] - k <= level[far[node]]) {
        k -= level[node] - (level[far[node]]);
        node = far[node];
      } else {
        k --;
        node = parent[node];
      }
    }
    if(node == 0)
      std::cout << -1 << '\n';
    else
      std::cout << node << '\n';
  }
  return 0;
}