#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define inf 1145141919
#define llinf 1145141919810364364
#define mod 1000000007

int max(int a,int b){if(a>b){return a;}return b;}
int min(int a,int b){if(a<b){return a;}return b;}
int round(int a,int b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
int ceil(int a,int b){if(a%b==0){return a/b;}return (a/b)+1;}
int gcd(int a,int b){int c;while(b!=0){c=a%b;a=b;b=c;}return a;}
int lcm(int a,int b){int c=gcd(a,b);a/=c;return a*b;}
int nCr(int a,int b){int i,r=1;for(i=1;i<=r;i++){r*=(a+1-i);r/=i;}return r;}
int fact(int a){int i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
int pow(int a,int b){int i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
long long llmax(long long a,long long b){if(a>b){return a;}return b;}
long long llmin(long long a,long long b){if(a<b){return a;}return b;}
long long llround(long long a,long long b){if((a%b)*2 >= b){return (a/b)+1;}return a/b;}
long long llceil(long long a,long long b){if(a%b==0){return a/b;}return (a/b)+1;}
long long llgcd(long long a,long long b){long long c;while(b!=0){c=a%b;a=b;b=c;}return a;}
long long lllcm(long long a,long long b){long long c=llgcd(a,b);a/=c;return a*b;}
long long llnCr(long long a,long long b){long long i,r=1;for(i=1;i<=r;i++){r*=(a+1-i);r/=i;}return r;}
long long llfact(long long a){long long i,r=1;for(i=1;i<=a;i++){r*=i;}return r;}
long long llpow(long long a,long long b){long long i,r=1;for(i=1;i<=b;i++){r*=a;}return r;}
double dbmax(double a,double b){if(a>b){return a;}return b;}
double dbmin(double a,double b){if(a<b){return a;}return b;}
int sortfncsj(const void *a,const void *b){if(*(int *)a>*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int sortfnckj(const void *a,const void *b){if(*(int *)a<*(int *)b){return 1;}if(*(int *)a==*(int *)b){return 0;}return -1;}
int llsortfncsj(const void *a,const void *b){if(*(long long *)a>*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int llsortfnckj(const void *a,const void *b){if(*(long long *)a<*(long long *)b){return 1;}if(*(long long *)a==*(long long *)b){return 0;}return -1;}
int dbsortfncsj(const void *a,const void *b){if(*(double *)a>*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}
int dbsortfnckj(const void *a,const void *b){if(*(double *)a<*(double *)b){return 1;}if(*(double *)a==*(double *)b){return 0;}return -1;}

typedef struct{
    int coor;
    int node;
} data;
typedef struct{
    int leng;
    int node1;
    int node2;
} way;

int datsortfncsj(const void *a,const void *b){if(((*(data *)a)->coor)>((*(data *)b)->coor){return 1;}if(((*(data *)a)->coor)==((*(data *)b)->coor){return 0;}return -1;}
int waysortfncsj(const void *a,const void *b){if(((*(way *)a)->leng)>((*(way *)b)->leng){return 1;}if(((*(way *)a)->leng)==((*(way *)b)->leng){return 0;}return -1;}

int main(void){
     int x[131072],y[131072],n,i,j,check[131072]={0},st=1;
    long long res=0;
    data xdat[131072],ydat[131072];
    way waydat[524288];
    scanf("%d",&n);
    for(i=0;i<n;i++){scanf("%d%d",&x[i],&y[i]);}
    for(i=0;i<n;i++){
        xdat[i].coor=x[i];xdat[i].node=i;
        ydat[i].coor=y[i];ydat[i].node=i;
    }
    qsort(xdat,n,sizeof(data),datsortfncsj);
    qsort(ydat,n,sizeof(data),datsortfncsj);
    for(i=0;i<n-1;i++){
        waydat[2*i].leng=xdat[i+1].coor-xdat[i].coor;
        waydat[2*i].node1=xdat[i].node;
        waydat[2*i].node2=xdat[i+1].node;
        waydat[2*i+1].leng=ydat[i+1].coor-ydat[i].coor;
        waydat[2*i+1].node1=ydat[i].node;
        waydat[2*i+1].node2=ydat[i+1].node;
    }
    qsort(waydat,2*(n-1),sizeof(way),waysortfncsj);
    for(i=0;i<2*(n-1);i++){
        if(i==0){
            check[waydat[i].node1]=1;
            check[waydat[i].node2]=1;
            res+=waydat[i].leng;
        }
        else{
            if(check[waydat[i].node1] == check[waydat[i].node2] && check[waydat[i].node1] != 0){continue;}
            if(check[waydat[i].node1] == check[waydat[i].node2] && check[waydat[i].node1] == 0){
                res+=waydat[i].leng;st++;check[waydat[i].node1]=st;check[waydat[i].node2]=st;
            }
            else{
                res+=waydat[i].leng;
                for(j=0;j<n;j++){if(check[waydat[i].node1] == check[j]){check[j] = check[waydat[i].node2]}}
            }
        }
    }
    printf("%lld\n",res);
    return 0;
}