#include<bits/stdc++.h>
using namespace std;
const int N=210;
int n,s,e;
int vis[N];
int a[N];
int flag;
int ans=0x3f3f3f3f;
void dfs(int u,int step)
{
	if(step>ans) return;
	vis[u]=1;
	if(u==e)
	{
		ans=min(ans,step);
		flag=1;
		return;
	}
	int x=a[u];
	if(u-x>=1&&vis[u-x]==0) dfs(u-x,step+1);
	if(u+x<=n&&vis[u+x]==0) dfs(u+x,step+1);
	return;
}
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>s>>e;
	for(int i=1;i<=n;i++) cin>>a[i];
	dfs(s,0);
	if(!flag) cout<<-1;
	else cout<<ans;
	return 0;
}