#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template <typename T> inline bool chmax(T &a, T b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> inline bool chmin(T &a, T b) {
  return ((a > b) ? (a = b, true) : (false));
}

int main(){
  ll x,y;cin >> x >> y;
  map<pl,ll> memo;
  memo[{x,y}]=0;
  queue<pl> que;que.push({x,y});
  while(!que.empty()){
    pl q=que.front();que.pop();
    if(memo[q]>=5)continue;
    if(!memo.count({q.second,q.first})){
      memo[{q.second,q.first}]=memo[q]+1;
      que.push({q.second,q.first});
    }
    if(!memo.count({q.first+q.second,q.first-q.second})){
      memo[{q.first+q.second,q.first-q.second}]=memo[q]+1;
      que.push({q.first+q.second,q.first-q.second});
    }
  }
  ll ans=INF;
  for(auto p:memo){
    if(p.first.first==p.first.second){
      chmin(ans,p.second);
    }
  }
  cout << (ans!=INF? ans:-1) << endl;
}