#include<bits/stdc++.h>
#define inf 0x3f3f3f3f
using namespace std;
int N,A,B,a[2005],ans=inf;
bool vis[2005];
void deepfs(int x,int t)
{
	if(x<1 or x>N or vis[x] or t>ans) return ;
	if(x==B)
	{
		ans=min(t,ans);
		return ;
	}
	vis[x]=1;
	deepfs(x-a[x],t+1);
	deepfs(x+a[x],t+1);
	vis[x]=0;
}
int main()
{
	cin>>N>>A>>B;
	for(int i=1;i<=N;i++) cin>>a[i];
	deepfs(A,0);
	if(ans==inf) cout<<"-1";
	else cout<<ans;
	return 0;
}