#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,m;
    cin>>n>>m;
    if(n==2){
        if(m<2){
	cout<<2<<endl;
	}else{
	cout<<1<<endl;
	}
        return 0;
    }
    if(m<n)cout<<-1<<endl;
    else cout<<1<<endl;
    return 0;
}