#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=210;
int n,A,B,a[N],ans;
queue<int> q;
void bfs(int k){
	if(k==B) return ;
	ans++;
	int t=k+a[k];
	if(t>0&&t<=n) q.push(t);
	t=k-a[k];
	if(t>0&&t<=n) q.push(t);
	while(!q.empty()){
		t=q.front();
		q.pop();
		bfs(t);
	}
	return ;
}
signed main(){
	cin>>n>>A>>B;
	for(int i=1;i<=n;++i) cin>>a[i];
	bfs(A);
	cout<<ans<<endl;
	return 0;
}