#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;

int n,A,B;
int now;
int s[210];
int ans[210],flag[210];
queue<int>floor;

int main()
{
	scanf("%d%d%d",&n,&A,&B);
	for(int i=1;i<=n;i++)
	{	scanf("%d",&s[i]);	}
	memset(flag,0,sizeof(flag));
	memset(ans,0,sizeof(ans));
	ans[A]=0,flag[A]=1;
	floor.push(A);
	
	while( !floor.empty() )
	{	now=floor.front();
		floor.pop();
		if(now==B)break;
		if( now+s[now]>0 && now+s[now]<=n && flag[now+s[now]]==0 )
		{	floor.push(now+s[now]);
			ans[now+s[now]]=ans[now]+1;
			flag[now+s[now]]=1;
		}
		
		if( now-s[now]>0 && now-s[now]<=n && flag[now+s[now]]==0 )
		{	floor.push(now-s[now]);
			ans[now+s[now]]=ans[now]+1;
			flag[now-s[now]]=1;
		}
	}
	
	if(now==B)
	{	printf("%d",ans[B]);	} 
	else
	{	printf("-1");	}
	
	return 0;
}