52分代码（乱取名的变量）：

#include<bits/stdc++.h>
using namespace std;
int lift[205],last_floor=1024;
int walk,pd[205];
void run(int start,int last,int times){
	walk=lift[start];
	pd[start]=1;
	if(walk==0) return;
	if(start+walk==last){
		if(last_floor>times) last_floor=times;return;
	}
	if(start-walk==last){
		if(last_floor>times) last_floor=times;return;
	}
	if(lift[start+walk]!=-1&&pd[start+walk]==0){
		 run(start+walk,last,times+1);
	}
	if(lift[start-walk]!=-1&&pd[start-walk]==0){
		 run(start-walk,last,times+1);
	}
}
int main(){
    int n,a,b;
	cin>>n>>a>>b;
	for(int i=0;i<205;i++){
		lift[i]=-1;
	}
	for(int i=1;i<=n;i++){
		cin>>lift[i];
	} 
	run(a,b,1);
	if(last_floor!=1024) cout<<last_floor;
	else cout<<"-1";
	return 0;
}