#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cwchar>
#include <cwctype>
#include <complex.h>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <fenv.h>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <inttypes.h>
#include <limits>
#include <list>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <stdbool.h>
#include <stdint.h>
#include <tgmath.h>
#include <utility>
#include <vector>

using namespace std;

#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;

struct node{
	int pos , step;
};

int n , l , r , a[N]; 
bool v[N];

void bfs(int x){
	queue<node> q;
	q.push((node){x , 0});
	v[x] = 1;
	
	while(!q.empty()){
		node top = q.front();
		q.pop();
		
		if(top.pos == r){
			cout << top.step;
			exit(0);
		}
		
		if(top.pos + a[top.pos] <= n && !v[top.pos + a[top.pos]]){
			v[top.pos + a[top.pos]] = 1;
			q.push((node){top.pos + a[top.pos] , top.step + 1});
		}
		if(top.pos - a[top.pos] >= 1 && !v[top.pos - a[top.pos]]){
			v[top.pos - a[top.pos]] = 1;
			q.push((node){top.pos - a[top.pos] , top.step + 1});
		} 
	}
}
int main() {	
	cin >> n >> l >> r;
	for(int i = 1;i <= n;i++){
		cin >> a[i];
	}
	bfs(l);
	cout << -1;
    return 0;
}