import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.*;

public class Main {
    static InputStream is;
    static PrintWriter out;
    static String INPUT = "";

    void solve() {
        class Node {
            int x, y, i, xi, yi;

            Node(int x, int y, int i) {
                this.x = x;
                this.y = y;
                this.i = i;
            }

            int d(Node n) {
                return Math.min(Math.abs(x - n.x), Math.abs(y - n.y));
            }
        }
        int n = ni();
        Node l[] = new Node[n];
        Node xl[] = new Node[n];
        Node yl[] = new Node[n];
        for (int i = 0; i < n; ++i) {
            Node a = new Node(ni(), ni(), i);
            l[i] = a;
            xl[i] = a;
            yl[i] = a;
        }
        Arrays.sort(xl, (a, b) -> a.x - b.x);
        Arrays.sort(yl, (a, b) -> a.y - b.y);
        for (int i = 0; i < n; ++i) {
            xl[i].xi = i;
            yl[i].yi = i;
        }
        int mincost[] = new int[n];
        Arrays.fill(mincost, Integer.MAX_VALUE / 2);
        long v = 0;
        class State {
            int i, cost;

            State(int i, int cost) {
                this.i = i;
                this.cost = cost;
            }
        }
        PriorityQueue<State> queue = new PriorityQueue<>((a, b) -> a.cost - b.cost);
        queue.add(new State(0, 0));
        while (queue.size() > 0) {
            State s = queue.poll();
            if (s.cost > mincost[s.i]) continue;
            Node x = l[s.i];
            mincost[s.i] = -1;
            v += s.cost;
            if (x.xi > 0) {
                Node t = xl[x.xi - 1];
                int c = x.d(t);
                if (mincost[t.i] > c) {
                    mincost[t.i] = c;
                    queue.add(new State(t.i, c));
                }
            }
            if (x.xi + 1 < n) {
                Node t = xl[x.xi + 1];
                int c = x.d(t);
                if (mincost[t.i] > c) {
                    mincost[t.i] = c;
                    queue.add(new State(t.i, c));
                }
            }
            if (x.yi > 0) {
                Node t = yl[x.yi - 1];
                int c = x.d(t);
                if (mincost[t.i] > c) {
                    mincost[t.i] = c;
                    queue.add(new State(t.i, c));
                }
            }
            if (x.yi + 1 < n) {
                Node t = yl[x.yi + 1];
                int c = x.d(t);
                if (mincost[t.i] > c) {
                    mincost[t.i] = c;
                    queue.add(new State(t.i, c));
                }
            }
        }
        out.println(v);
    }

    public static void main(String[] args) throws Exception {
        long S = System.currentTimeMillis();
        is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);

        new Main().solve();
        out.flush();
        long G = System.currentTimeMillis();
        // tr(G - S + "ms");
    }

    private static boolean eof() {
        if (lenbuf == -1) return true;
        int lptr = ptrbuf;
        while (lptr < lenbuf)
            if (!isSpaceChar(inbuf[lptr++])) return false;

        try {
            is.mark(1000);
            while (true) {
                int b = is.read();
                if (b == -1) {
                    is.reset();
                    return true;
                } else if (!isSpaceChar(b)) {
                    is.reset();
                    return false;
                }
            }
        } catch (IOException e) {
            return true;
        }
    }

    private static byte[] inbuf = new byte[1024];
    static int lenbuf = 0, ptrbuf = 0;

    private static int readByte() {
        if (lenbuf == -1) throw new InputMismatchException();
        if (ptrbuf >= lenbuf) {
            ptrbuf = 0;
            try {
                lenbuf = is.read(inbuf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (lenbuf <= 0) return -1;
        }
        return inbuf[ptrbuf++];
    }

    private static boolean isSpaceChar(int c) {
        return !(c >= 33 && c <= 126);
    }

    private static int skip() {
        int b;
        while ((b = readByte()) != -1 && isSpaceChar(b))
            ;
        return b;
    }

    private static double nd() {
        return Double.parseDouble(ns());
    }

    private static char nc() {
        return (char) skip();
    }

    private static String ns() {
        int b = skip();
        StringBuilder sb = new StringBuilder();
        while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    private static char[] ns(int n) {
        char[] buf = new char[n];
        int b = skip(), p = 0;
        while (p < n && !(isSpaceChar(b))) {
            buf[p++] = (char) b;
            b = readByte();
        }
        return n == p ? buf : Arrays.copyOf(buf, p);
    }

    private static char[][] nm(int n, int m) {
        char[][] map = new char[n][];
        for (int i = 0; i < n; i++)
            map[i] = ns(m);
        return map;
    }

    private static int[] na(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = ni();
        return a;
    }

    private static int ni() {
        int num = 0, b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
            ;
        if (b == '-') {
            minus = true;
            b = readByte();
        }

        while (true) {
            if (b >= '0' && b <= '9') {
                num = num * 10 + (b - '0');
            } else {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }

    private static long nl() {
        long num = 0;
        int b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
            ;
        if (b == '-') {
            minus = true;
            b = readByte();
        }

        while (true) {
            if (b >= '0' && b <= '9') {
                num = num * 10 + (b - '0');
            } else {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }

    private static void tr(Object... o) {
        System.err.println(Arrays.deepToString(o));
    }
}