#include<iostream>
#include<queue>
using namespace std;
struct node{
    int x,y;
};
queue <node> q;
int n,a,b,k[205],xnew,ynew;
bool vis[205];
int bfs()
{
    q.push({a,0});
    vis[a]=true;
    while (!q.empty())
    {
        int x=q.front().x,y=q.front().y;
        if (x==b) return y;
        q.pop();
        xnew=x+k[x];
        ynew=y+1;
        if (xnew>0 && xnew<=n && vis[xnew]==false)
        {
            vis[xnew]=true;
            q.push({xnew,ynew});
        }
        xnew=x-k[x];
        ynew=y+1;
        if (xnew>0 && xnew<=n && vis[xnew]==false)
        {
            vis[xnew]=true;
            q.push({xnew,ynew});
        }
    }
    return -1;
}
int main()
{
    cin>>n>>a>>b;
    for (int i=1;i<=n;i++)
    {
        cin>>k[i];
        vis[i]=false;
    }
    cout<<bfs();
    return 0;
}

但运行时间长