validbst

#include<bits/stdc++.h>
using namespace std;


// You should only implement the function given below

class node{
public:
    int val;
    node* left;
    node* right;

    node(int val):val(val),left(nullptr),right(nullptr){}
};


bool solution(node* root){
       // write your code here
}


int main(){
    int n,r; cin >> n >> r;
    vector<node*>vec(n+1);
    for(int i = 1; i <= n; i++){
            int t; cin >> t;
            vec[i] = new node(t);
    }
    for(int i = 1; i <= n; i++){
            int x,y; cin >> x >> y;
            if(x != -1){
                vec[i] -> left = vec[x];
            }if(y != -1){
                vec[i] -> right = vec[y];
            }
    }
    cout << (solution(vec[r])?"YES":"NO") << endl;

}