#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int main() {
int x1,x2,y1,y2,a,b,c,tg,x,y,k,n,i;
cin >> x1 >> y1 >> x2 >> y2;
x=abs(x2-x1);
y=abs(y2-y1);
tg=y/x;
n=0;
k=0;
if (x1==x2)
{
	n=abs(y2-y1);
}
if (y1==y2)
{
	n=abs(x2-x1);
}
while (x1<x2)
{
	k++;
	x1++;
	y=tg*k;
	i=abs(y);
	if (y=i)
	n++;
}
while (x1>x2)
{
	k++;
	x2++;
	y=tg*k;
	i=int(y);
	if (y=i)
	n++;
}
n=n+1;
cout <<n;
}