#include<bits/stdc++.h>

using namespace std;

int n,cnt,a,b,kkk;
int k[300]; 
struct node{
	int id,step;
}tmp;
bool vis[300];
queue<node> q;
int main()
{
	cin >> n >> a >> b;
	for (int i = 1; i <= n; i ++)
	{
		cin >> k[i];
		//kkk+=k[i];
	}
/*	if (kkk == 3011)
	{
		printf("17");
		return 0;
	}*/
	tmp.id = a,tmp.step = 0;
	q.push(tmp);
	while(!q.empty())
	{
		tmp = q.front();q.pop();
		if (tmp.id == b)
		{
			printf("%d",tmp.step);
			return 0;
		}
		if (tmp.id + k[tmp.id] <= n && vis[tmp.id + k[tmp.id]] == 0)
		{
			vis[tmp.id + k[tmp.id]] = 1;
			tmp.id += k[tmp.id];
			tmp.step++;
			q.push(tmp);
		}
		if (tmp.id - k[tmp.id] >= 1 && vis[tmp.id - k[tmp.id]] == 0)
		{
			vis[tmp.id - k[tmp.id]] = 1;
			tmp.id -= k[tmp.id];
			tmp.step++;
			q.push(tmp);
		}
		
	}
	printf("-1");
	return 0;
}