#include<bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define pii pair<int,int> 
#define pli pair<long long,int>
#define pll pair<long long,long long> 
#define pb push_back
#define mk make_pair
#define show(x) cerr<<#x<<x<<endl;
using namespace std;

ll x,y;

int main(){
  cin>>x>>y;
  if(x==y){
    cout<<0<<endl;
    return 0;
  }
  if(x==0 || y==0){
    if(x==0){
      cout<<2<<endl;
    }else cout<<1<<endl;
    return 0;
  }
  if(abs(x)==abs(y)){
    ll temp=x;
    x=x+y;
    y=temp-y;
    if(x==0)cout<<3<<endl;
    else cout<<4<<endl;
  }else{
    cout<<-1<<endl;
  }
  return 0;
}