//代码：

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

int n,a,b,v[210];
bool book[210]={};

struct node
{
    int tim,floor;
};

int bfs()
{
    queue<node>c;
    c.push({0,a});
    while(c.size())
    {
        node fl=c.front();
        c.pop();
        if(fl.floor==b)return fl.tim;
        if(fl.floor-v[fl.floor]>0&&book[fl.floor-v[fl.floor]]!=1)
        {
            c.push({fl.floor-v[fl.floor],fl.tim+1});
            book[fl.floor-v[fl.floor]]=1;
        }
        if(fl.floor+v[fl.floor]<=n&&book[fl.floor+v[fl.floor]]!=1)
        {
            c.push({fl.floor+v[fl.floor],fl.tim+1});
            book[fl.floor-v[fl.floor]]=1;
        }
    }
    return -1;
}

int main()
{
    cin>>n>>a>>b;
    for(int i=1;i<=n;i++)cin>>v[i];
    cout<<bfs();
    return 0;
}