#include<bits/stdc++.h>
using namespace std;
bool f[100000]={false};
int n,a,b,k[100000],ans=0,i=0;

bool dfs(int start){
	if(!(start>-1&&start<=200))return false;
	if(start==b){ans++;return true;}
	if(f[start]==true)return false;
	f[start]=true;
	while(i<=n){
		++i;
		if(dfs(start+k[i])){ans++;return true;}
		if(dfs(start-k[i])){ans++;return true;}
	}
	return false;
} 
int main(){
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>k[i];
	}
	if(dfs(a-1)){cout<<ans<<endl;}
	else cout<<-1<<endl;
	
	return 0;
}