#include <bits/stdc++.h>
using namespace std;
const int N = 2240;
struct node{
    int a,b,c;
}sp[N];
int dis[N],u[N],a,b,n;
int main()
{
    cin >> n >> a >> b;
    int cnt = 1;
    for(int i = 1,v ; i <= n ; i++){
        cin >> v;
        if(i+v<=n) sp[cnt++] = {i,i+v,1};
        if(i-v>=1) sp[cnt++] = {i,i-v,1};
    }
    memset(dis,0x3f,sizeof dis);
    dis[a] = 0;
    for(int k = 1 ; k <= n; k ++ ){
        memcpy(u,dis,sizeof dis);
        for(int i = 1 ; i <= cnt ; i++) {
            dis[sp[i].b] = min(dis[sp[i].b],u[sp[i].a]+sp[i].c);
        }
    } 
    if(dis[b]>=0x3f3f3f3f/2) cout << -1 << endl;
    else cout << dis[b] << endl;
    return 0; 
}