#include<bits/stdc++.h>
using namespace std;
int n,a,ans=2147483647,b,k[205],p[205]; 
void dfs(int x,int y){
	if(ans<y) return;
	if(x==b){
		ans=min(ans,y);
		return;
	}
	p[x]=1;
	if(x+k[x]<=n&&p[x+k[x]]==0){
		dfs(x+k[x],y+1);
	}
	if(x-k[x]>=1&&p[x-k[x]]==0){
		dfs(x-k[x],y+1);
	}
	p[x]=0;
}
int main(){
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>k[i];
	}
	dfs(a,0);
	if(ans==2147483647){
		cout<<-1;
	}
	else{
		cout<<ans;
	}
	return 0;
}