using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    static readonly int INF = (int)1e9;
    static readonly string Impossible = "Odekakedekinai..";
    static readonly int[] DR = { 0, 1, 0, -1 };
    static readonly int[] DC = { 1, 0, -1, 0 };

    public void Solve()
    {
        int W = Reader.Int(), H = Reader.Int(), N = Reader.Int();
        var table = Reader.IntTable(N * 2);
        long[][] row = new long[H][];
        long[][] col = new long[W][];

        for (int r = 0; r < H; r++)
            row[r] = new long[(W + 63) / 64];
        for (int c = 0; c < W; c++)
            col[c] = new long[(H + 63) / 64];

        for (int ti = 1; ti < N * 2; ti += 2)
        {
            var t = table[ti];
            for (int i = 0; i + 1 < t.Length; i++)
            {
                int r = t[i] / W, c = t[i] % W;
                int nr = t[i + 1] / W, nc = t[i + 1] % W;
                if (Math.Sign(nr - r) != 0)
                    BitArrayOr(col[c], Math.Min(r, nr), Math.Max(r, nr));
                else
                    BitArrayOr(row[r], Math.Min(c, nc), Math.Max(c, nc));
            }
        }
        bool[, ,] G = new bool[H, W, 4];
        for (int r = 0; r < H; r++)
            for (int c = 0; c + 1 < W; c++)
                if ((row[r][c / 64] >> c % 64 & 1) == 1 && (row[r][(c + 1) / 64] >> (c + 1) % 64 & 1) == 1)
                {
                    G[r, c, 0] = true;
                    G[r, c + 1, 2] = true;
                }
        for (int c = 0; c < W; c++)
            for (int r = 0; r + 1 < H; r++)
                if ((col[c][r / 64] >> r % 64 & 1) == 1 && (col[c][(r + 1) / 64] >> (r + 1) % 64 & 1) == 1)
                {
                    G[r, c, 1] = true;
                    G[r + 1, c, 3] = true;
                }

        int ans = BFS(G, H, W);
        Console.WriteLine(ans == INF ? Impossible : ans + "");
    }

    private void BitArrayOr(long[] A, int from, int to)
    {
        if ((from >> 6) == (to >> 6))
        {
            A[from >> 6] |= (1L << to - from + 1) - 1 << from;
            return;
        }
        int a = (from + 63) >> 6;
        int b = to >> 6;
        A[from >> 6] |= (1L << 64 - from) - 1 << (from & 63);
        for (int i = a; i < b; i++) A[i] = -1L;
        A[to >> 6] |= (1L << (to + 1 & 63)) - 1;
    }

    private int BFS(bool[, ,] G, int H, int W)
    {
        var minCost = new int[H, W];
        for (int r = 0; r < H; r++)
            for (int c = 0; c < W; c++)
                minCost[r, c] = INF;
        minCost[0, 0] = 0;
        var que = new Queue<int>();
        que.Enqueue(0); que.Enqueue(0);

        while (que.Count > 0)
        {
            int r = que.Dequeue(), c = que.Dequeue();
            for (int d = 0; d < DR.Length; d++)
                if (G[r, c, d])
                {
                    int nr = r + DR[d], nc = c + DC[d];
                    int nextCost = minCost[r, c] + 1;
                    if (nextCost < minCost[nr, nc])
                    {
                        if (nr == H - 1 && nc == W - 1) return nextCost;
                        minCost[nr, nc] = nextCost;
                        que.Enqueue(nr); que.Enqueue(nc);
                    }
                }
        }

        return INF;
    }

}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Next()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}