<span style="font-size:24px;">#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<queue>
using namespace std;
 
const int maxn = 201;
int n, a, b;
int kp[maxn];
bool mark[maxn];
struct Node {
    int floor;
    int tme;
};
 
int BFS() {
    memset(mark, false, sizeof(mark));
    queue<Node> Q;
    Node first, next_up, next_down;
    first.tme = 0;
    first.floor = a;
    Q.push(first);
    mark[a] = true;  //标记
 
    while (!Q.empty()) {
        first = Q.front();
        Q.pop();
 
        if (first.floor == b) {
            return first.tme;
        }
        next_up.floor = first.floor + kp[first.floor];
        if (next_up.floor <= n && !mark[next_up.floor ]) {
            next_up.tme = first.tme + 1;
            mark[next_up.floor] = true;
            Q.push(next_up);
        }
        next_down.floor = first.floor - kp[first.floor];
        if (next_down.floor >= 1 && !mark[next_down.floor]) {
            next_down.tme = first.tme + 1;
            mark[next_down.floor] = true;
            Q.push(next_down);
        }
    }
    return -1;
}  
 
int main() {
 
    while (~scanf("%d", &n), n ) {
        scanf("%d%d", &a, &b);
        for (int i = 1; i <= n; i++) {
            scanf("%d", &kp[i]);
        }                         //输入
        int res = BFS();
        printf("%d\n", res);
    }
}</span>