#include<iostream>
#include<queue>
using namespace std;
struct node{
	int n,k,l;
	bool s;
};
int main(){
	queue<node> q;
	node o[500],t;
	int n,a,b;
	cin>>n>>a>>b;
	for(int i=0;i<n;i++){
		cin>>o[i].k;
		o[i].n=i+1;
		if(i+1==a) o[i].s==false;
		else o[i].s==true;
	}
	t.n=a;
	t.k=o[a-1].k;
	t.s=false;
	t.l=0;
	q.push(t);
	while(!q.empty()){
		node top=q.front();
		q.front().s=false;
		q.pop();
		if(b==top.n){
			cout<<top.l;
			return 0;
		}
		if(top.k<top.n&&o[top.n-top.k-1].s){
			o[top.n-top.k-1].l=top.l+1;
			q.push(o[top.n-top.k-1]);
		}
		if(top.k+top.n<=n){
			o[top.n+top.k-1].l=top.l+1;
			q.push(o[top.n+top.k-1]);
		}
	}
	cout<<-1;
	return 0;
}

测试点1-5,9,14,15 WA,测试点8TLE