#include<bits/stdc++.h>
using namespace std;


#define li          long long int
#define rep(i,to)   for(li i=0;i<((li)(to));i++)
#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)
#define pb          push_back
#define sz(v)       ((li)(v).size())
#define bgn(v)      ((v).begin())
#define eend(v)     ((v).end())
#define allof(v)    (v).begin(), (v).end()
#define dodp(v,n)       memset(v,(li)n,sizeof(v))
#define bit(n)      (1ll<<(li)(n))
#define mp(a,b)     make_pair(a,b)
#define rin rep(i,n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1


#define idp if(DBGP)
#define F first
#define S second
#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl
#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl
#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl
#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl
#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl
#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl
#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl
#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl
#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl
#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)
#define p2p(x)      idp p2((x).F, (x).S)
#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}
#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}
#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}
#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}

#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]
#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}

typedef pair<li, li> PI;

li n;
pair<PI, li> p[100100];

vector<pair<li, PI>> edges;

class UnionFind {
public:
    UnionFind(li n) {
        parent.resize(n);
        rin{
            parent[i] = i;
        }
    }
    inline bool Same(li x, li y) {
        return (find(x) == find(y));
    }
    inline void Merge(li x, li y) {
        li parent_x = find(x);
        li parent_y = find(y);
        parent[parent_x] = parent_y;
    }
private:
    inline li find(li x) {
        if (parent[x] == x)return x;
        else return (parent[x] = find(parent[x]));
    }
    vector<li> parent;
};

int main() {
    cin >> n;
    rin{
        cin >> p[i].F.F >> p[i].F.S;
        p[i].S = i;
    }

    sort(p, p + n);
    rep(i, n - 1) {
        edges.pb({p[i + 1].F.F - p[i].F.F, {p[i].S, p[i + 1].S}});
    }
    sort(p, p + n, [](pair<PI, li>& a, pair<PI, li>& b) {
        return a.F.S < b.F.S;
    });
    rep(i, n - 1) {
        edges.pb({abs(p[i + 1].F.S - p[i].F.S), {p[i].S, p[i + 1].S}});
    }
    li res = 0;

    UnionFind uf(n);
    sort(allof(edges));
    for (auto && edge : edges) {
        if (!uf.Same(edge.S.F, edge.S.S)) {
            uf.Merge(edge.S.F, edge.S.S);
            res += edge.F;
        }
    }
    cout << res << endl;

    return 0;
}

Measured memory_bytes: 10864