#include <cstdio>

 #include <cmath>

 #include <algorithm>

 int f[][]={{,,,,},{,,,,},{,,,,},{,,,,},{,,,,}};

 int main()

 {

     int a,b,c,d,x,y,ans=;

     scanf("%d%d%d%d",&a,&b,&c,&d);

     x=abs(a-c); y=abs(b-d);

     while ((x>)||(y>) )

     {

         if (x>y) {x-=; y-=;}

         else {x-=; y-=; }

         x=abs(x);

         y=abs(y);

         ans++;

     }

     if ((x<=)&&(y<=)) {printf("%d",ans+f[x][y]); return ;}

     while ((x==)&&(y>=))

     {

         x-=; y-=; ans++;

     }

     while ((y==)&&(x>=))

     {

         x-=; y-=; ans++;

     }

     while ((x==)&&(y>=))

     {

         y-=; ans+=;

     }

     while ((y==)&&(x>=))

     {

         x-=; ans+=;

     }

     ans+=f[x][y];

     printf("%d",ans);

 }