#include<fstream.h>
#include<math.h>
int m,n,i,a,b,s1,s2,s;
struct sir {int x,y;};
sir v[5];
int main()
{
ifstream f("orase.in");
ofstream g("orase.out");

f>>m>>n;

f>>v[1].x>>v[1].y;
f>>v[2].x>>v[2].y;

s=abs(v[1].x-v[2].x) + v[1].y+v[2].y;

 for(i=3;i<=n;i++)

  { f>>a>>b;

    s1=abs(a-v[1].x) + b+ v[1].y;

    s2=abs(a-v[2].x) + b+ v[2].y;

    if(s1>s2 && s1>s) { v[2].x=a; v[2].y=b; s=s1; }

     if(s2>s1 && s2>s) { v[1].x=a; v[1].y=b; s=s2; }
  }
g<<s;
f.close();
g.close();
return 0;
}