#include<bits/stdc++.h>

using namespace std;

#define int long long
#define ar array
#define vt vector
#define pb push_back
#define all(c) (c).begin(), (c).end()
#define sz(x) (int)(x).size()

#define F_OR(i, a, b, s) for (int i=(a); (s)>0?i<(b):i>(b); i+=(s))
#define F_OR1(e) F_OR(i, 0, e, 1)
#define F_OR2(i, e) F_OR(i, 0, e, 1)
#define F_OR3(i, b, e) F_OR(i, b, e, 1)
#define F_OR4(i, b, e, s) F_OR(i, b, e, s)
#define GET5(a, b, c, d, e, ...) e
#define F_ORC(...) GET5(__VA_ARGS__, F_OR4, F_OR3, F_OR2, F_OR1)
#define FOR(...) F_ORC(__VA_ARGS__)(__VA_ARGS__)
#define EACH(x, a) for (auto& x: a)

template<class T>
bool umin(T &a, const T &b) {
    return b < a ? a = b, 1 : 0;
}

template<class T>
bool umax(T &a, const T &b) {
    return a < b ? a = b, 1 : 0;
}

template<class A>
void read(vt<A> &v);

template<class A, size_t S>
void read(ar<A, S> &a);

template<class T>
void read(T &x) {
    cin >> x;
}

void read(double &d) {
    string t;
    read(t);
    d = stod(t);
}

void read(long double &d) {
    string t;
    read(t);
    d = stold(t);
}

template<class H, class... T>
void read(H &h, T &... t) {
    read(h);
    read(t...);
}

template<class A>
void read(vt<A> &x) {
    EACH(a, x)read(a);
}

template<class A, size_t S>
void read(array<A, S> &x) {
    EACH(a, x)read(a);
}

string to_string(char c) {
    return string(1, c);
}

string to_string(bool b) {
    return b ? "true" : "false";
}

string to_string(const char *s) {
    return string(s);
}

string to_string(string s) {
    return s;
}

string to_string(vt<bool> v) {
    string res;
    FOR(sz(v))res += char('0' + v[i]);
    return res;
}

template<size_t S>
string to_string(bitset<S> b) {
    string res;
    FOR(S)res += char('0' + b[i]);
    return res;
}

template<class T>
string to_string(T v) {
    bool f = 1;
    string res;
    EACH(x, v) {
        if (!f)
            res += ' ';
        f = 0;
        res += to_string(x);
    }
    return res;
}

template<class A>
void write(A x) {
    cout << to_string(x);
}

template<class H, class... T>
void write(const H &h, const T &... t) {
    write(h);
    write(t...);
}

void print() {
    write("\n");
}

template<class H, class... T>
void print(const H &h, const T &... t) {
    write(h);
    if (sizeof...(t))
        write(' ');
    print(t...);
}

template<class T, class U>
void vti(vt<T> &v, U x, size_t n) {
    v = vt<T>(n, x);
}

template<class T, class U>
void vti(vt<T> &v, U x, size_t n, size_t m...) {
    v = vt<T>(n);
    EACH(a, v)vti(a, x, m);
}

const int mxN = 1e5;
vt<ar<int, 3>> E;
int link[mxN], sz[mxN];

int find(int x) {
    if (link[x] == x) {
        return x;
    }
    return find(link[x]);
}

bool same(int a, int b) {
    return find(a) == find(b);
}

void unite(int a, int b) {
    a = find(a);
    b = find(b);
    
    if (sz[a] < sz[b]) swap(a, b);
    
    sz[a] += sz[b];
    link[b] = a;
}

void solve() {
    int n;
    read(n);
    
    vt<ar<int, 2>> xv, yv;
    
    map<ar<int, 2>, int> mp;
    FOR(n) {
        int x, y;
        read(x, y);
        mp[{x, y}] = i;
        xv.pb({x, y});
        yv.pb({y, x});
    }
    
    sort(all(xv));
    sort(all(yv));
    
    FOR(i, 1, n) {
        int x = abs(xv[i][0] - xv[i - 1][0]);
        int y = mp[{xv[i - 1][0], xv[i - 1][1]}];
        int z = mp[{xv[i][0], xv[i][1]}];
        E.pb({x, y, z});
        x = abs(yv[i][0] - yv[i - 1][0]);
        y = mp[{yv[i - 1][1], yv[i - 1][0]}];
        z = mp[{yv[i][1], yv[i][0]}];
        E.pb({x, y, z});
    }
    
    sort(all(E));
    FOR(n) {
        link[i] = i;
        sz[i] = 1;
    }
    
    int ans = 0;
    EACH(x, E) {
        if (!same(x[1], x[2])) {
            ans += x[0];
            unite(x[1], x[2]);
        }
    }
    
    print(ans);
    
}

int32_t main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    
    int tt = 1;
    //read(tt);
    FOR(tt) {
        //write("Case #", i + 1, ": ");
        solve();
        
    }
    
}



Measured memory_bytes: 20504