#include<iostream>
#include<queue>
using namespace std;
int main()
{
	queue<int>a;int A,B,n,i,u;
	cin>>n>>A>>B;
	int floor[n+1],time[n+1];
	bool yon[n+1]={true},v=true;yon[A]=false;
	for(i=1;i<=n;i++)
	{
		cin>>floor[i];
	}
	a.push(A);time[A]=0;
	while(!a.empty())
	{
		u=a.front();a.pop();
		if(u==B)
		{
			cout<<time[u];
			return 0;
		}
		if(yon[u+floor[u]]&&u+floor[u]<=n&&u-floor[u]>0)
		{
			a.push(u+floor[u]);
			yon[u+floor[u]]=false;
			time[u+floor[u]]=time[u]+1;
		}
		if(yon[u-floor[u]]&&u-floor[u]>0&&u-floor[u]<=n)
		{
			a.push(u-floor[u]);
			yon[u-floor[u]]=false;
			time[u-floor[u]]=time[u]+1;
		}
	}
	cout<<-1;
	return 0;
}