#include<bits/stdc++.h>
using namespace std;
int a[1005];
bool  vis[205];
int n,m,b,flag = -1;
struct node {
	int y, step;
};
queue<node> q;
void bfs(int y){
	vis[y] = 1;
	q.push((node){y,0});
	while(!q.empty()){
		node front = q.front();
		q.pop();
		
		if(front.y == b){
			flag = front.step;
			return;
		}
		int ny = front.y + a[front.y];
		int nt = front.step + 1;
		if(vis[ny] == 0 && ny > 0 && ny <= 200){
			vis[ny] = 1;
			q.push((node){ny,nt});
		}
		
		ny = front.y - a[front.y];
		if(vis[ny] == 0 && ny > 0 && ny <= 200){
			vis[ny] = 1;
			q.push((node){ny,nt});
		}
	}
}
int main(){
	cin >> n >> m >> b;
	for(int i = 1;i <= n;i++){
		cin >> a[i];
	}
	bfs(m);
	cout << flag;
	
}