#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;
}

#include <iostream>
using namespace std;
int w[20003];
int n,a,b;
int minn=0x7ffffff;
bool ans[2003];
bool check(int x){
	return (x<=n&&x>=1);
}
void dfs(int now,int sum){
	if(now==b) minn=min(minn,sum);
    if(sum>minn) return;
	ans[now]=1;
	if(check(now+w[now])&&(!ans[now+w[now]]))
		dfs(now+w[now],sum+1);
	if(check(now-w[now])&&(!ans[now-w[now]]))
		dfs(now-w[now],sum+1);
	ans[now]=0;
    return ;
}
int main(){
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>w[i];
	}
	dfs(a,0);
	if(minn!=0x7ffffff) cout<<minn;
	else cout<<-1;
	return 0;
}