#include <bits/stdc++.h>
using namespace std;
int main()
{
    int x1,x2,y1,y2,julipingfang;
    cin >> x1 >> y1 >> x2 >> y2;
    julipingfang = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
    for (int i = sqrt(julipingfang);i >= 1;i--)
    {
        if (julipingfang % (i * i) == 0)
        {
            cout << i + 1;
            return 0;
        }
    }
}