#include<bits/stdc++.h>
using namespace std;
int k[210],len[210],d[210];
int main(){
	int n,a,b;
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		scanf("%d",&k[i]);
	} 
	memset(len ,63,sizeof(len));
	len[a]=0;
	int h=1,r=1;
	d[1]=a;
	while(h<=r);{
		int u=d[h];
		for(int j=1;j<=2;j++){
			int v;
			if(j==1)v=u+k[u];
			else if(j==2)v=u-k[u];
			if(0<v&&v<=n&&len[u]+1<len[v]){
				len[v]=len[u]+1;
				if(v==b)break;
				d[++r]=v;
			}
		}
		h++;
	}
	if(len[b]>10000)cout<<-1<<endl;
	else cout<<len[b]<<endl;
	return 0;
}