#include<bits/stdc++.h>
using namespace std;
int n,b,a,ans;
int x[201];
bool y[201],w;
queue<int> q;
void bfs(){
	while(!q.empty()){
		ans++;
		int xx=q.front();
		int tx=xx+x[xx];
		int ty=xx-x[xx];
		if(tx==a||ty==a){
			cout<<ans;
			w=1;
			return;
		}
		if(tx>=1&&tx<=n&&y[tx]==0){
			q.push(tx);
			y[tx]=1;
		}
		if(ty>=1&&ty<=n&&y[ty]==0){
			q.push(ty);
			y[ty]=1;
		}
		q.pop();
	}
}
int main(){
	cin>>n>>b>>a;
	for(int i=1;i<=n;i++)
	{
		cin>>x[i];
	}
	q.push(b);
	y[b]=1;
	bfs();
	if(w==0)
	{
		cout<<-1;
	}
}
/**************************************************************
	Problem: 1819
	User: wuyunfeng
	Language: C++
	Result: Wrong Answer
****************************************************************/