#include <iostream>
using namespace std;
int w[20003];
int n,a,b;
int minn=0x7ffffff;
bool ans[2003];
bool check(int x){
	return (x<=n&&x>=1);
}
void dfs(int now,int sum){
	if(now==b) minn=min(minn,sum);
    if(sum>minn) return;
	ans[now]=1;
	if(check(now+w[now])&&(!ans[now+w[now]]))
		dfs(now+w[now],sum+1);
	if(check(now-w[now])&&(!ans[now-w[now]]))
		dfs(now-w[now],sum+1);
	ans[now]=0;
    return ;
}
int main(){
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>w[i];
	}
	dfs(a,0);
	if(minn!=0x7ffffff) cout<<minn;
	else cout<<-1;
	return 0;
}