// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;



#define fi first

#define se second

const int inf = 1e9 + 7;

int n, par[100010], ans = 0;

pair <pair <int, int>, int> a[100010]; bool dis[100010];

priority_queue<pair <int, pair <int, int> >, vector<pair <int, pair <int, int> > >, greater<pair <int, pair <int, int> > > > wl1, wl2;

int find(int a) {

	return (par[a] < 0 ? a : par[a] = find(par[a]));

}

void unionset(int a, int b) {

	int c = find(a), d = find(b);

	if(par[c] < par[d]) par[c] += par[d], par[d] = c;

	else par[d] += par[c], par[c] = d;

}

int main() {

	memset(par, -1, sizeof(par));

	scanf("%d", &n);

	for(int i = 0; i < n; i++) {

		scanf("%d%d", &a[i].fi.fi, &a[i].fi.se);

		a[i].se = i;

	}

	sort(a, a + n);

	for(int i = 0; i < n-1; i++) {

		wl1.push({a[i+1].fi.fi - a[i].fi.fi, {a[i].se, a[i+1].se}});

		swap(a[i].fi.fi, a[i].fi.se);

	}

	swap(a[n-1].fi.fi, a[n-1].fi.se);

	sort(a, a + n);

	for(int i = 0; i < n-1; i++) wl2.push({a[i+1].fi.fi - a[i].fi.fi, {a[i].se, a[i+1].se}});

	for(int i = 1; i < n; i++) {

		while(find(wl1.top().se.fi) == find(wl1.top().se.se)) wl1.pop();

		while(find(wl2.top().se.fi) == find(wl2.top().se.se)) wl2.pop();

		int d1 = inf, d2 = inf, u1, u2, v1, v2;

		if(not wl1.empty()) d1 = wl1.top().fi, u1 = wl1.top().se.fi, v1 = wl1.top().se.se;

		if(not wl2.empty()) d2 = wl2.top().fi, u2 = wl2.top().se.fi, v2 = wl2.top().se.se;

		if(d1 < d2) {

			unionset(u1, v1);

			ans += d1;

		}

		else {

			unionset(u2, v2);

			ans += d2;

		}

	}

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

}

// Faster C++ solution for the same problem (measured speedup: 1.3782456933789922x):
// #define FNAME "template"



#define NDEBUG



#include <bits/stdc++.h>

using namespace std;



typedef long long inte;

const int maxn = 100005;



#ifndef NDEBUG

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

#else

#    define dprint(x) (NULL)

#endif



template<typename T>

inline void readFig(T& x)

{

#   ifdef FTREAD

        static int c = 0;

        int op = 1;

        x = 0;

        while (!isdigit(c)) {

            if (c == '-')

                op = -1;

            c = getchar();

        }

        while (isdigit(c)) {

            x *= 10;

            x += c - '0';

            c = getchar();

        }

        x *= op;

#   else

        cin >> x;

#   endif

}



int N, M;

struct Edge {

    int u, v, w;

} edges[maxn * 2];

inline bool operator < (const Edge &a, const Edge &b)

{

    return a.w < b.w;

}



int par[maxn];

int getPar(int x)

{

    static int st[maxn];

    int stop = 0;

    while (par[x] != x) {

        x = par[x];

        st[stop++] = x;

    }

    while (stop--)

        par[st[stop]] = x;

    return x;

}

inline inte genMST()

{

    for (int i = 1; i <= N; ++i)

        par[i] = i;

    int cnt = 0;

    inte ans = 0;

    for (int i = 1; i <= M; ++i) {

        int u = getPar(edges[i].u), v = getPar(edges[i].v);

        if (u != v) {

            par[u] = v;

            ++cnt;

            ans += edges[i].w;

            dprint(ans);

        }

    }

    //assert(cnt == N - 1);

    return ans;

}



struct City {

    int x, y, id;

} cities[maxn];



inline bool compx(const City &a, const City &b)

{

    return a.x < b.x;

}

inline bool compy(const City &a, const City &b)

{

    return a.y < b.y;

}

inline int getdis(const City &a, const City &b)

{

    return min(abs(a.x - b.x), abs(a.y - b.y));

}



inline void solve()

{

    readFig(N);

    for (int i = 1; i <= N; ++i) {

        readFig(cities[i].x); readFig(cities[i].y);

        cities[i].id = i;

    }

    sort(cities + 1, cities + N + 1, compx);

    for (int i = 1; i < N; ++i) {

        edges[++M].u = cities[i].id;

        edges[M].v = cities[i + 1].id;

        edges[M].w = getdis(cities[i], cities[i + 1]);

    }

    sort(cities + 1, cities + N + 1, compy);

    for (int i = 1; i < N; ++i) {

        edges[++M].u = cities[i].id;

        edges[M].v = cities[i + 1].id;

        edges[M].w = getdis(cities[i], cities[i + 1]);

    }

    sort(edges + 1, edges + M + 1);

    cout << genMST() << endl;

}



signed main()

{

#   ifdef FNAME

        freopen(FNAME".in", "r", stdin);

        freopen(FNAME".out", "w", stdout);

#   endif

#   ifndef FTREAD

    	ios::sync_with_stdio(false);

    	cin.tie(0);

#   endif



#   ifdef MULTEST

        int T;

        readFig(T);

        while (T--)

            solve();

#   else

        solve();

#   endif



#   ifdef FNAME

        fclose(stdin);

        fclose(stdout);

#   endif

    	return 0;

}