#include <stdio.h>
#include <stdlib.h>

typedef struct { int x,y; } tBod;

tBod B[150000];
int P,i,sum;

int xcmp(const void *a, const void *b){
  tBod *aa,*bb;
  aa=(tBod *)a; bb=(tBod *)b;
  if ((aa->x)!=(bb->x)) return ((aa->x)-(bb->x));
  if ((aa->y)!=(bb->y)) return ((aa->y)-(bb->y));
  return 0;
}

int ycmp(const void *a, const void *b){
  tBod *aa,*bb;
  aa=(tBod *)a; bb=(tBod *)b;
  if ((aa->y)!=(bb->y)) return ((aa->y)-(bb->y));
  if ((aa->x)!=(bb->x)) return ((aa->x)-(bb->x));
  return 0;
}

int main(void){
  while (1) {
    scanf("%d ",&P);
    if (!P) break;
    for (i=0;i<P;i++) scanf("%d %d ",&B[i].x,&B[i].y); 
    sum=0;
    qsort(B,P,sizeof(tBod),xcmp); 
    for (i=0;i<P/2;i++) sum+=abs(B[2*i+1].y - B[2*i].y); 
    qsort(B,P,sizeof(tBod),ycmp); 
    for (i=0;i<P/2;i++) sum+=abs(B[2*i+1].x - B[2*i].x); 
    printf("The length of the fence will be %d units.\n",sum); 
  } 
  return 0;
}