#include<bits/stdc++.h>
using namespace std;

const int N = 210;

int n,a,b,k[N],dis[N];

void dfs(int u,int step){
	dis[u]=step;
	int v=u-k[u];
	if(1<=v&&step+1<dis[v]){
		dfs(v,step+1);
	}
	v=u+k[u];
	if(v<=n&&step+1<dis[v]){
		dfs(v,step+1);
	}
	return;
}

int main(){
	freopen("lift.in","r",stdin);
	freopen("lift.out","w",stdout);
	memset(dis,0x3f,sizeof(dis));
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++)
		cin>>k[i];
	dfs(a,0);
	cout<<(dis[b]==0x3f3f3f3f?-1:dis[b]);
	return 0;
}