#include <iostream>
#include <vector>
using namespace std;
struct TreeNode{
    int val;
    TreeNode* left;
    TreeNode* right;

    TreeNode(int _val): val(_val), left(nullptr), right(nullptr) {}
};
TreeNode* buildTree(const vector<int>& arr, int& idx){
    if(arr.empty()) return nullptr;
    if(idx >= arr.size() || arr[idx] == 0){
        idx++;
        return nullptr;
    }

    TreeNode* node = new TreeNode(arr[idx++]);
    node->left = buildTree(arr, idx);
    node->right = buildTree(arr, idx);

    return node;
}
TreeNode* LCA = nullptr;
TreeNode* check(TreeNode* root, int val1, int val2){
    if(root == nullptr) return nullptr;
    if(root->val == val1 || root->val == val2) return root;

    TreeNode* lc = check(root->left, val1, val2);
    TreeNode* rc = check(root->right, val1, val2);

    if(lc && rc) return root;
    return (lc ? lc : rc);

}
int main(){
    //前序增强输入
    int n;
    cin >> n;
    vector<int> arr(n);
    for(int i = 0; i < n; i++){
        cin >> arr[i];
    }
    int pa, pb;
    cin >> pa >> pb;
    int p = 0;
    TreeNode* root = buildTree(arr, p);
    LCA = check(root, pa, pb);
    cout << LCA->val << endl;
    return 0;
}