#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 #include<cmath>

 #include<queue>

 #define dbg(x) cerr << #x << " = " << x <<endl

 using namespace std;

 typedef long long ll;

 typedef double db;

 typedef pair<int,int> pii;

 template<typename T>inline T _min(T A,T B){return A<B?A:B;}

 template<typename T>inline T _max(T A,T B){return A>B?A:B;}

 template<typename T>inline char MIN(T&A,T B){return A>B?(A=B,):;}

 template<typename T>inline char MAX(T&A,T B){return A<B?(A=B,):;}

 template<typename T>inline void _swap(T&A,T&B){A^=B^=A^=B;}

 template<typename T>inline T read(T&x){

     x=;int f=;char c;while(!isdigit(c=getchar()))if(c=='-')f=;

     while(isdigit(c))x=x*+(c&),c=getchar();return f?x=-x:x;

 }

 const int N=+;

 struct thxorz{

     int u,v,w;

     thxorz(int u=,int v=,int w=):u(u),v(v),w(w){}

     inline bool operator <(const thxorz&A)const{return w<A.w;}

 }e[N<<];

 int n,tot;

 struct stothx{int x,y,id;}A[N];

 inline bool cmp1(stothx a,stothx b){return a.x<b.x;}

 inline bool cmp2(stothx a,stothx b){return a.y<b.y;}

 int anc[N];

 ll ans;

 inline int get_anc(int x){return anc[x]==x?x:anc[x]=get_anc(anc[x]);}

 int main(){//freopen("test.in","r",stdin);//freopen("test.ans","w",stdout);

     read(n);

     for(register int i=;i<=n;++i)read(A[i].x),read(A[i].y),A[i].id=i;

     sort(A+,A+n+,cmp1);

     for(register int i=;i<n;++i)e[++tot]=thxorz(A[i].id,A[i+].id,A[i+].x-A[i].x);

     sort(A+,A+n+,cmp2);

     for(register int i=;i<n;++i)e[++tot]=thxorz(A[i].id,A[i+].id,A[i+].y-A[i].y);

     sort(e+,e+tot+);

     for(register int i=;i<=n;++i)anc[i]=i;

     for(register int i=;i<=tot;++i)if(get_anc(e[i].u)^get_anc(e[i].v))ans+=e[i].w,anc[anc[e[i].u]]=anc[e[i].v];

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

     return ;

 }