#include<bits/stdc++.h>
using namespace std;
#define MAX 210
struct fff{
	int floor;
	int t;
}f;
int N,A,B;
int vis[MAX];
int a[MAX];
int main()
{
	queue<fff> q;
	cin>>N>>A>>B;
	for(int i=1;i<=N;++i)
	cin>>a[i];
	q.push({A,0});
	while(!q.empty())
	{
	f=q.front();
	vis[f.floor]=1;
	if(f.floor==B)
		{
		cout<<f.t;
		return 0;
		}
	q.pop();
	int x1=f.floor+a[f.floor];
	int x2=f.floor-a[f.floor];
	if(x1<=N)
	if(vis[x1]!=1)
		q.push({x1,++f.t});
	if(x2>0)
	if(vis[x2]!=1)
	 	q.push({x2,++f.t}); 
	}
	cout<<-1;
	return 0;
 }