#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define mod 1000000007

void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

ll binpow(ll x,ll y)/* (x^y)%p in O(log y) */{ll res=1;while (y > 0){if(y&1)res=(res*x);y = y>>1;x=(x*x);}return res;}
ll binpowmod(ll x,ll y,ll p)/* (x^y)%p in O(log y) */{ull res=1;x=x%p;while (y > 0){if(y&1)res=(res*x)%p;y = y>>1;x=(x*x)%p;}return res;}
ll mod_inverse(ll n,ll p)/* Returns n^(-1) mod p */{return binpowmod(n,p-2,p);}
ll gcd(ll x,ll y)
{
    if(y==0)
        return x;
    return gcd(y,x%y);
}
bool comp_pairs_by_s(pair<ll,ll> &x ,pair<ll,ll> &y)
{
    return x.second<y.second;
}
bool isPowerOfTwo (ll x)  
{  
    /* First x in the below expression is for the case when x is 0 */
    return x && (!(x&(x-1)));  
}

class cmp      //comparator for priority_queue 
{               //declaration: priority_queue<int,vector<int>,cmp>
public:         
    bool operator()(pair<int,int> A,pair<int,int> B)
    {
        if(abs(A.first-A.second)==abs(B.first-B.second))
            return A.first>B.first;
        return abs(A.first-A.second)<abs(B.first-B.second);
    }
};
// int prime[10000007]={0};
// void sieve(void)
// {
//  int i,j;
//  for(i=0;i<10000007;i++)
//         prime[i]=1;
//  prime[0]=0,prime[1]=0;
//  for(i=2;i<=sqrt(10000007);i++){
//      if(prime[i]==i){
//          for(j=i*i;j<10000007;j+=i){
//             if(!prime[j])
//                 prime[j]=0;
//          }
//      }
//  }
    
// }
void swap(ll &x,ll &y){
    int temp=x;
    x=y;
    y=temp;
}
  
unsigned int onesComplement(unsigned int n) 
{ 
   // Find number of bits in the given integer 
   int number_of_bits = floor(log2(n))+1; 
  
   // XOR the given integer with poe(2,  
   // number_of_bits-1 and print the result  
   return ((1 << number_of_bits) - 1) ^ n; 
}
bool comp(pair<ll,ll> x,pair<ll,ll> y)
{
    return x.second<y.second;
}

bool comp1(pair<ll,pair<ll,ll>> x,pair<ll,pair<ll,ll>> y)
{
    return x.first<y.first;
}
vector<int> p(100001);
int findp(int x){
    if(x==p[x])
        return x;
    return p[x]=findp(p[x]);
}
int unify(int x,int y)
{
    int x1=findp(x);
    int y1=findp(y);
    if(x1==y1)
        return 1;
    else{
        p[x1]=y1;
        return 0;
    }
}
void solve()
{   
    int n;
    cin>>n;
    vector<pair<ll,ll>> xy;
    vector<pair<ll,pair<ll,ll>>> edges;
    map<pair<ll,ll>,ll> cnt;
    for(int i=0;i<n;++i){
        ll x,y; cin>>x>>y;
        xy.push_back({x,y}); cnt[{x,y}]=i;
    }
    sort(xy.begin(),xy.end());
    for(int i=0;i<n-1;++i){
        ll cost=abs(xy[i+1].first-xy[i].first);
        edges.push_back({cost,{cnt[xy[i]],cnt[xy[i+1]]}});
    }    
    sort(xy.begin(),xy.end(),comp);
    for(int i=0;i<n-1;++i){
        ll cost=abs(xy[i+1].second-xy[i].second);
        edges.push_back({cost,{cnt[xy[i]],cnt[xy[i+1]]}});
    }  
    sort(edges.begin(),edges.end(),comp1);
    for(int i=0;i<n;++i)
        p[i]=i;
    ll ans=0;
    debug(edges);
    for(int i=0;i<edges.size();++i){
        int node=edges[i].second.first; int to=edges[i].second.second;
        int nodeid=findp(node); int toid=findp(to);
        //cout<<nodeid<<' '<<toid<<'\n';
        if(nodeid==toid) continue;
        if(unify(node,to))
            continue;
        ans+=edges[i].first;
    }
    //for(int i=0;i<n;++i) cout<<p[i]<<' ';
    cout<<ans;

}   
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); 
    solve();
}   



Measured memory_bytes: 19156