#include<bits/stdc++.h>
using namespace std;
int n,a,b,k[205],vis[205];
struct node{
	int f,s;
};
queue<node> q;
int main(){
	cin >> n >> a >> b;
	for(int i=1;i<=n;i++) cin >> k[i];
	q.push({a,0});
	vis[a]=1;
	while(!q.empty()){
		node now = q.front();
		q.pop();
		if(now.f == b){
			cout << now.s;
			return 0;
		}
		for(int i=-1;i<=1;i+=2){
			int nx = now.f+i*k[now.f];
			if(nx<1||nx>n||vis[nx]) continue;
			vis[nx]=1;
			q.push({nx,now.s+1}); 
		}
	}
	cout << -1;
	return 0;
}