P1135

#include<bits/stdc++.h>
using namespace std;
int n,a,b,m,ans,minn=1145;
vector<int> mapp[100005];
bool vis[100005],f;
void dfs(int x){
	if(x==b){
		minn=min(minn,ans);
		return;
	}
	for(int i=0;i<mapp[x].size();i++){
		if(!vis[mapp[x][i]]){
			vis[mapp[x][i]]=1;
			ans++;
			dfs(mapp[x][i]);
			ans--;
			//vis[mapp[x][i]]=0;
		}
	}
}
int main(){
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>m;
		if(i+m<=n&&m!=0){
			mapp[i].push_back(i+m);
		}
		if(i-m>=1&&m!=0){
			mapp[i].push_back(i-m);
		}
	}
	vis[a]=1;
	dfs(a);
	if(minn==1145){
		cout<<-1;
		return 0;
	}
	cout<<minn;
	return 0;
}