#include <bits/stdc++.h>
using namespace std;
int n,a,b,u[2],minn=1919810,book[100005],mapp[10005];
void dfs(int x,int step)
{
	book[x]=1;
	if(x==b)
	{
		minn=min(minn,step);
		return;
	}
	u[0]=x-mapp[x];
	u[1]=x+mapp[x];
	for(int i=0;i<2;i++)
	{
		if(u[i]<0)continue;
		if(book[u[i]]==0)
		{
			book[u[i]]=1;
			dfs(u[i],step+1);
		}
	}
}
int main()
{
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++)
	{
		cin>>mapp[i];
	}
	dfs(a,0);
	if(minn==1919810)cout<<-1;
	else cout<<minn;
	return 0;
}