#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  return gcd(b, a%b);    
}

// override function template of std::gcd
long long gcd(int a, int b) {
  return gcd((long long)a, (long long)b);
}

pair<int, int> norm(int x, int y) {
  int g = gcd(abs(x), abs(y));
  x /= g;
  y /= g;
  return {x, y};
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int x1, y1, x2, y2;
  cin >> x1 >> y1;
  cin >> x2 >> y2;

  auto n1 = norm(x1, y1), n2 = norm(x2, y2);
  
  int ret = max(abs(x1), abs(y1));
  if (abs(n1.first) == abs(n1.second)) {
    if (n1 == n2 && abs(x1) > abs(x2)) {
      ++ret;
    }
  }
  
  cout << ret << endl;
  
  return 0;
}