#include <iostream>
#include <queue>
#include <vector>
#include <climits>

using namespace std;

int main() {
    int N, A, B;
    cin >> N >> A >> B;
    vector<int> K(N + 1);
    for (int i = 1; i <= N; ++i) {
        cin >> K[i];
    }

    // 记录每层是否已访问
    vector<bool> visited(N + 1, false);
    // 队列存储当前层和到达该层的按键次数
    queue<pair<int, int>> q;
    q.push({A, 0});
    visited[A] = true;

    while (!q.empty()) {
        int current_floor = q.front().first;
        int steps = q.front().second;
        q.pop();

        if (current_floor == B) {
            cout << steps << endl;
            return 0;
        }
        // 尝试上楼
        int next_floor_up = current_floor + K[current_floor];
        if (next_floor_up <= N && !visited[next_floor_up]) {
            visited[next_floor_up] = true;
            q.push({next_floor_up, steps + 1});
        }
        // 尝试下楼
        int next_floor_down = current_floor - K[current_floor];
        if (next_floor_down >= 1 && !visited[next_floor_down]) {
            visited[next_floor_down] = true;
            q.push({next_floor_down, steps + 1});
        }
    }
    cout << -1 << endl;
    return 0;
}