#include <stdio.h>
#include <queue>
#include <map>
#include <algorithm>
#define pii pair<int,int>
#define ff first
#define ss second
using namespace std;
map<pii,int> mp;
queue<pii> q;
int main(){
int a,b,c,d;
scanf("%d %d %d %d",&a,&b,&c,&d);
if(a!=c && !c && b!=d && !d){printf("-1");return 0;}
mp[{0,0}]=0; q.push({0,0});
while(!q.empty()){
int pa=q.front().ff;
int pb=q.front().ss; q.pop();
int pd=mp[{pa,pb}];
if(pa==c && pb==d){printf("%d",pd);return 0;}
if(a && mp.find({0,pb})==mp.end()) mp[{0,pb}]=pd+1,q.push({0,pb});
if(b && mp.find({pa,0})==mp.end()) mp[{pa,0}]=pd+1,q.push({pa,0});
if(pa!=a){
if(mp.find({a,pb})==mp.end()) mp[{a,pb}]=pd+1,q.push({a,pb});
if(pa+pb>a && mp.find({a,pa+pb-a})==mp.end()) mp[{a,pa+pb-a}]=pd+1,q.push({a,pa+pb-a});
if(pa+pb<=a && mp.find({pa+pb,0})==mp.end()) mp[{pa+pb,0}]=pd+1,q.push({pa+pb,0});
}
if(pb!=b){
if(mp.find({pa,b})==mp.end()) mp[{pa,b}]=pd+1,q.push({pa,b});
if(pa+pb>b && mp.find({pa+pb-b,b})==mp.end()) mp[{pa+pb-b,b}]=pd+1,q.push({pa+pb-b,b});
if(pa+pb<=b && mp.find({0,pa+pb})==mp.end()) mp[{0,pa+pb}]=pd+1,q.push({0,pa+pb});
}
}
printf("-1");
return 0;
}
