#include<bits/stdc++.h>
using namespace std;
int sx[3][1001],ans=999,n,a,b;
bool m[1001]={0};
int bfs(int x,int r){
	bool q=0;
	int l=r;
	if(r>999){
		cout<<-1<<endl;
		exit(0);
	}
	if(x<1||x>n)
		return 2;
	if(x==b){
		ans=min(r,ans);
	}
	if(x+sx[1][x]==b&&m[x+sx[1][x]]==0||x+sx[2][x]==b&&m[x+sx[2][x]]==0){
		ans=min(r+1,ans);
		return 1;
	}
	for(int i=1;i<=2;i++){
		if((x+sx[i][x])<=n&&(x+sx[i][x])>0&&m[x+sx[i][x]]==0){//
			m[x+sx[i][x]]=1;
			int w;
			w=bfs(x+sx[i][x],l+1);
			if(w==1){
				q=1;
			}
			m[x+sx[i][x]]=0;
		}
	}
	if(q){
		return 1;
	}
	return 2;
}
int main(){
	int x;
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>sx[1][i];
		sx[2][i]=0-sx[1][i];
	}
	int w;
	w=bfs(a,0);
	if(w==2){
		cout<<-1<<endl;
	}
	else{
		cout<<ans<<endl;
	}
	return 0;
}