#include<iostream>
#include<queue>
using namespace std;
struct lift{
    int floor,times;
};
int n,a,b,k[100001];
bool flag=false,visited[100001];
queue<lift>que;
lift tmp;
int l(){
    lift temp={a,0};
    que.push(temp);
    while(!que.empty()){
        tmp=que.front();
        que.pop();
        if(tmp.floor==b)return tmp.times;
        for(int i=-1;i<=1;i+=2){
            int tmpf=tmp.floor+k[tmp.floor]*i;
            if(tmpf>=1&&tmpf<=n&&!visited[tmpf]){
                lift tmptmp={tmpf,tmp.times+1};
                que.push(tmptmp);
                visited[tmpf]=true;
            }
        }
    }
}
int main(){
    cin>>n>>a>>b;
    for(int i=1;i<=n;i++)cin>>k[i];
    visited[a]=true;
    int ans=l();
    if(tmp.floor==b)cout<<ans<<endl;
    else cout<<-1<<endl;
    return 0;
}