#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
vector<vector<int> > graph(30050);
int a, b, n, t, curr_time = 0, answer = 0;
struct vertex
{
    int time_in, time_out, h;
};
vertex vertices[30050];
void dfs(int v, int h)
{
    vertices[v].time_in = curr_time;
    vertices[v].h = h;
    for (int i = 0; i < graph[v].size(); i++)
    {
        curr_time++;
        dfs(graph[v][i], h + 1);
        curr_time++;
    }
    vertices[v].time_out = curr_time;
}
int main(){
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
#endif
    cin >> n >> a >> b;
    for (int i = 1; i < n; i++)
    {
        cin >> t;
        graph[t - 1].push_back(i);
    }
    dfs(0, 0);
    for (int i = 1; i < n; i++)
        if (vertices[i].time_in <= vertices[a - 1].time_in && vertices[a - 1].time_out <= vertices[i].time_out && vertices[i].time_in <= vertices[b - 1].time_in && vertices[b - 1].time_out <= vertices[i].time_out && vertices[answer].h < vertices[i].h)
            answer = i;
    cout << answer + 1;
    return 0;
}