#include<bits/stdc++.h>

 using namespace std;

 struct Point{

     double x, y;

     Point(double x=, double y=):x(x), y(y){}

 };

 typedef Point Vector;

 Vector operator + (Vector A, Vector B){

     return Vector(A.x+B.x, A.y+B.y);

 }

 Vector operator - (Point A, Point B){

     return Vector(A.x-B.x, A.y-B.y);

 }

 Vector operator * (Vector A, double p){

     return Vector(A.x * p, A.y * p);

 }

 Vector operator / (Vector A, double p){

     return Vector(A.x / p, A.y / p);

 }

 bool operator < (const Point& a, const Point& b){

     return a.x < b.x || (a.x == b.x && a.y < b.y);

 }

 double Cross(Vector A, Vector B)

 {

     return A.x * B.y - A.y * B.x;

 }

 int ConvexHull(Point* p, int n, Point* ch)

 {

     sort(p, p+n);

     int m=;

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

     {

         while(m >  && Cross(ch[m-] - ch[m-], p[i] - ch[m-]) <= )  m--;

         ch[m++] = p[i];

     }

     int k = m;

     for(int i = n-;i >= ;i--)

     {

         while(m > k && Cross(ch[m-] - ch[m-], p[i] - ch[m-]) <= )  m--;

         ch[m++] = p[i];

     }

     if(n > )  m--;

     return m;

 }

 const int maxn =  + ;

 int n;

 Point points[maxn * ], ch[maxn * ];

 int main()

 {

     //printf("%lf\n", sqrt(2) * 4);

     while(scanf("%d", &n) == )

     {

         double x, y;

         int cnt = ;

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

         {

             scanf("%lf%lf", &x, &y);

             points[cnt].x = x+, points[cnt++].y = y;

             points[cnt].x = x-, points[cnt++].y = y;

             points[cnt].x = x, points[cnt++].y = y+;

             points[cnt].x = x, points[cnt++].y = y-;

         }

         int pcnt = ConvexHull(points, cnt, ch);

         double ans = ;

         //sort(ch, ch + pcnt);

         //for(int i = 0;i < pcnt;i++)  printf("%d: %lf  %lf\n", i, ch[i].x, ch[i].y);

         double dx = fabs(ch[].x - ch[pcnt-].x);

         double dy = fabs(ch[].y - ch[pcnt-].y);

         if(dx > dy)  swap(dx, dy);

         ans += dx * sqrt();

         ans += (dy - dx);

         for(int i = ;i < pcnt;i++)

         {

             double dx = fabs(ch[i].x - ch[i-].x);

             double dy = fabs(ch[i].y - ch[i-].y);

             if(dx > dy)  swap(dx, dy);

             ans += dx * sqrt();

             ans += (dy - dx);

             //printf("%lf\n", ans);

         }

         printf("%lf\n", ans);

     }

     return ;

 }