#include<cstdio>
using namespace std;
int n,a,b;
int minn=1E9;
int k[240];
void dfs(int f,int cnt){
	if(f==b){
		if(cnt<minn){
			minn=cnt;
		}
		return;
	}
	if(k[f]+f<=n)
		dfs(k[f]+f,cnt+1);
	if(f-k[f]>=1)
		dfs(f-k[f],cnt+1);
}
int main()
{
	scanf("%d%d%d",&n,&a,&b);
	for(int i=1;i<=n;i++)
		scanf("%d",&k[i]);
	dfs(a,0);
	if(minn==10E9){
		printf("-1");
		return 0;
	}
	printf("%d",minn);
}

https://www.luogu.com.cn/record/46761118