using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using Number = System.Int64;
namespace Program
{
    public class Solver
    {
        public void Solve()
        {
            for (;;)
            {
                var n = sc.Integer();
                var m = sc.Integer();
                if (n == 0) return;
                var G = Enumerate(n * m, x => new List<int>());
                for (int i = 0; i < n; i++)
                {
                    for (int j = 0; j < m - 1; j++)
                        if (sc.Integer() == 0)
                        {
                            G[i * m + j].Add(i * m + j + 1);
                            G[i * m + j + 1].Add(i * m + j);
                        }
                    for (int j = 0; i != n - 1 && j < m; j++)
                        if (sc.Integer() == 0)
                        {
                            G[i * m + j].Add((i + 1) * m + j);
                            G[(i + 1) * m + j].Add(i * m + j);
                        }
                }
                Func<int, int, int> f = (pos, not) =>
                {
                    var dist = Enumerate(n * m, z => 1 << 20);
                    dist[pos] = 0;
                    var q = new Queue<int>(); q.Enqueue(pos);
                    while (q.Count > 0)
                    {
                        var p = q.Dequeue();
                        for (int j = 0; j < G[p].Count; j++)
                        {
                            var to = G[p][j];
                            if (p == pos && to == not) continue;
                            if (dist[to] > dist[p] + 1) { dist[to] = dist[p] + 1; q.Enqueue(to); }
                        }
                    }
                    return dist[n * m - 1];
                };
                var dp = Enumerate(n * m, y => 1 << 20);
                dp[n * m - 1] = 0;
                var pq = new PriorityQueue<KeyValuePair<int, int>>((l, r) => l.Value.CompareTo(r.Value));
                pq.Enqueue(new KeyValuePair<int, int>(n * m - 1, 0));
                while (pq.Count > 0)
                {
                    var p = pq.Dequeue();
                    //Debug.WriteLine("{0} {1} {2}", p.Key / m, p.Key % m, p.Value);
                    if (dp[p.Key] < p.Value) continue;
                    foreach (var to in G[p.Key])
                    {
                        var cost = p.Value + 1;
                        var dost = f(to, p.Key);
                        cost = Math.Max(cost, dost);
                        if (dp[to] > cost)
                        {
                            dp[to] = cost;
                            pq.Enqueue(new KeyValuePair<int, int>(to, cost));
                        }
                    }

                }
                if (dp[0] >= 1 << 20) dp[0] = -1;
                IO.Printer.Out.WriteLine(dp[0]);
            }
        }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex
{
    static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
    //static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer: StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n'; b = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != 0 && b != '-' && (b < '0' || '9' < b));
            if (b == 0) return long.MinValue;
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion

#region BinaryHeap
public class PriorityQueue<T>
{
    readonly List<T> heap = new List<T>();
    readonly Comparison<T> cmp;
    public PriorityQueue() : this(Comparer<T>.Default) { }
    public PriorityQueue(IComparer<T> comparer) : this(comparer.Compare) { }
    public PriorityQueue(Comparison<T> comparison) { cmp = comparison; }
    public void Enqueue(T item)
    {

        var i = heap.Count;
        heap.Add(item);
        while (i > 0)
        {
            var p = (i - 1) / 2;
            if (cmp(heap[p], item) <= 0)
                break;
            heap[i] = heap[p];
            i = p;
        }
        heap[i] = item;

    }
    public T Dequeue()
    {
        var ret = heap[0];
        var i = 0;
        var x = heap[heap.Count - 1];

        while ((i * 2) + 1 < heap.Count - 1)
        {
            var a = i * 2 + 1;
            var b = i * 2 + 2;
            if (b < heap.Count - 1 && cmp(heap[b], heap[a]) < 0) a = b;
            if (cmp(heap[a], x) >= 0)
                break;
            heap[i] = heap[a];
            i = a;
        }
        heap[i] = x;
        heap.RemoveAt(heap.Count - 1);
        return ret;

    }
    public T Peek() { return heap[0]; }
    public int Count { get { return heap.Count; } }
    public bool Any() { return heap.Count > 0; }
    public T[] Items
    {
        get
        {
            var ret = heap.ToArray();
            Array.Sort(ret, cmp);
            return ret;
        }
    }
}
#endregion


Measured memory_bytes: 10960