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

long long n, a, b;
long long c[210];
bool f [330];

struct s{
	long long floor;
	long long step;
};

void bfs (){
	queue <s> p;
	s temp;
	temp.floor = a;
	temp.step = 0;
	p.push (temp);
	while (!p.empty()){
		s now = p.front ();
		long long floor = now.floor, step = now.step;
		long long sh = floor + c[floor], xi = floor - c[floor];
		p.pop ();
		if (floor == b){
			cout << step;
			return ;
		}
		if (sh >= 1 && sh <= n && !f[sh]){
			f[sh] = true;
			s temp;
			temp.floor = sh;
			temp.step = step + 1;
			p.push (temp);
		}
		if (xi >= 1 && xi <= n && !f[xi]){
			f[xi] = true;
			s temp;
			temp.floor = xi;
			temp.step = step + 1;
			p.push (temp);
		}
	}
	cout << -1;
	return ;
}

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