using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static System.Math;
using System.Text;
using System.Threading;
using System.Globalization;
using System.Runtime.CompilerServices;
using Library;

namespace Program
{
    public static class ProblemD
    {
        static bool SAIKI = true;
        static public int numberOfRandomCases = 0;
        static public void MakeTestCase(List<string> _input, List<string> _output, ref Func<string[], bool> _outputChecker)
        {
        }
        static public void Solve()
        {
            var N = NN;
            var M = NN;
            var S = NSList(N);
            var flow = new LIB_Flow(N * M + 2);
            Func<long, long, long> convToVtx = (x, y) => x * M + y;
            Func<long, (long, long)> convToPos = vtx => (vtx / M, vtx % M);
            var startVtx = N * M;
            var goalVtx = startVtx + 1;
            for (var i = 0; i < N; i++)
            {
                for (var j = 0; j < M; j++)
                {
                    if (S[i][j] == '#') continue;
                    if ((i + j) % 2 == 0)
                    {
                        flow.AddPath(startVtx, convToVtx(i, j), 1);
                        if (i > 0 && S[i - 1][j] != '#') flow.AddPath(convToVtx(i, j), convToVtx(i - 1, j), 1);
                        if (j > 0 && S[i][j - 1] != '#') flow.AddPath(convToVtx(i, j), convToVtx(i, j - 1), 1);
                        if (i < N - 1 && S[i + 1][j] != '#') flow.AddPath(convToVtx(i, j), convToVtx(i + 1, j), 1);
                        if (j < M - 1 && S[i][j + 1] != '#') flow.AddPath(convToVtx(i, j), convToVtx(i, j + 1), 1);
                    }
                    else flow.AddPath(convToVtx(i, j), goalVtx, 1);
                }
            }
            var res = flow.FordFulkerson(startVtx, goalVtx);
            Console.WriteLine(res.maxflow);
            var ans = Repeat(0, N).Select(_ => Repeat('.', M).ToArray()).ToArray();
            for (var i = 0; i < N; i++)
            {
                for (var j = 0; j < M; j++)
                {
                    if (S[i][j] == '#') ans[i][j] = '#';
                    else if ((i + j) % 2 == 0)
                    {
                        foreach (var toVtx in res.fromToCost[convToVtx(i, j)].Where(e => e.Value > 0))
                        {
                            if (toVtx.Key >= N * M) continue;
                            var pos = convToPos(toVtx.Key);
                            if (pos.Item1 == i && pos.Item2 < j)
                            {
                                ans[i][pos.Item2] = '>';
                                ans[i][j] = '<';
                            }
                            else if (pos.Item1 == i && pos.Item2 > j)
                            {
                                ans[i][j] = '>';
                                ans[i][pos.Item2] = '<';
                            }
                            else if (pos.Item1 < i && pos.Item2 == j)
                            {
                                ans[pos.Item1][j] = 'v';
                                ans[i][j] = '^';
                            }
                            else
                            {
                                ans[i][j] = 'v';
                                ans[pos.Item1][j] = '^';
                            }
                        }
                    }
                }
            }
            foreach (var item in ans) Console.WriteLine(item.Join());
        }
        class Printer : StreamWriter
        {
            public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
            public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { base.AutoFlush = false; }
            public Printer(Stream stream, Encoding encoding) : base(stream, encoding) { base.AutoFlush = false; }
        }
        static LIB_FastIO fastio = new LIB_FastIODebug();
        static public void Main(string[] args) { if (args.Length == 0) { fastio = new LIB_FastIO(); Console.SetOut(new Printer(Console.OpenStandardOutput())); } if (SAIKI) { var t = new Thread(Solve, 134217728); t.Start(); t.Join(); } else Solve(); Console.Out.Flush(); }
        static long NN => fastio.Long();
        static double ND => fastio.Double();
        static string NS => fastio.Scan();
        static long[] NNList(long N) => Repeat(0, N).Select(_ => NN).ToArray();
        static double[] NDList(long N) => Repeat(0, N).Select(_ => ND).ToArray();
        static string[] NSList(long N) => Repeat(0, N).Select(_ => NS).ToArray();
        static long Count<T>(this IEnumerable<T> x, Func<T, bool> pred) => Enumerable.Count(x, pred);
        static IEnumerable<T> Repeat<T>(T v, long n) => Enumerable.Repeat<T>(v, (int)n);
        static IEnumerable<int> Range(long s, long c) => Enumerable.Range((int)s, (int)c);
        static IOrderedEnumerable<T> OrderByRand<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x, _ => xorshift);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderBy<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderBy(x.OrderByRand(), selector);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x) => Enumerable.OrderByDescending(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderByDescending<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderByDescending(x.OrderByRand(), selector);
        static IOrderedEnumerable<string> OrderBy(this IEnumerable<string> x) => x.OrderByRand().OrderBy(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderBy(selector, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<string> OrderByDescending(this IEnumerable<string> x) => x.OrderByRand().OrderByDescending(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderByDescending(selector, StringComparer.OrdinalIgnoreCase);
        static string Join<T>(this IEnumerable<T> x, string separator = "") => string.Join(separator, x);
        static uint xorshift { get { _xsi.MoveNext(); return _xsi.Current; } }
        static IEnumerator<uint> _xsi = _xsc();
        static IEnumerator<uint> _xsc() { uint x = 123456789, y = 362436069, z = 521288629, w = (uint)(DateTime.Now.Ticks & 0xffffffff); while (true) { var t = x ^ (x << 11); x = y; y = z; z = w; w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)); yield return w; } }
    }
}
namespace Library {
    class LIB_Flow
    {
        LIB_Dict<int, long>[] path;
        int N;
        public class FlowResult
        {
            public long maxflow;
            public LIB_Dict<int, long>[] fromToCost;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Flow(long n)
        {
            N = (int)n;
            path = Enumerable.Repeat(0, N).Select(_ => new LIB_Dict<int, long>()).ToArray();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void AddPath(long a, long b, long c)
        {
            path[a][(int)b] += c;
            path[b][(int)a] += 0;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public FlowResult FordFulkerson(long s, long t)
        {
            var f = Enumerable.Repeat(0, N).Select(_ => new LIB_Dict<int, long>()).ToArray();
            for (var i = 0; i < N; i++) foreach (var item in path[i]) f[i][item.Key] = item.Value;
            var done = new long[N];
            var counter = 1L;
            Func<int, long, long> dfs = null;
            dfs = (vtx, c) =>
            {
                done[vtx] = counter;
                if (vtx == t) return c;
                foreach (var item in f[vtx])
                {
                    if (done[item.Key] == counter) continue;
                    if (item.Value == 0) continue;
                    var flow = dfs(item.Key, Min(c, item.Value));
                    if (flow == 0) continue;
                    f[vtx][item.Key] -= flow;
                    f[item.Key][vtx] += flow;
                    return flow;
                }
                return 0;
            };
            var sum = 0L;
            for (long flow; (flow = dfs((int)s, long.MaxValue)) > 0; ++counter) sum += flow;
            for (var i = 0; i < path.Length; i++) foreach (var to in path[i]) f[i][to.Key] = to.Value - f[i][to.Key];
            return new FlowResult { maxflow = sum, fromToCost = f };
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public FlowResult Dinic(long s, long t)
        {
            var f = Enumerable.Repeat(0, N).Select(_ => new LIB_Dict<int, long>()).ToArray();
            for (var i = 0; i < N; i++) foreach (var item in path[i]) f[i][item.Key] = item.Value;
            var level = new int[N];
            Func<bool> reset = () =>
            {
                level = new int[N];
                var q = new Queue<int>();
                level[s] = 1;
                q.Enqueue((int)s);
                while (q.Count > 0)
                {
                    var v = q.Dequeue();
                    foreach (var item in f[v])
                    {
                        if (item.Value > 0 && level[item.Key] == 0)
                        {
                            level[item.Key] = level[v] + 1;
                            q.Enqueue(item.Key);
                        }
                    }
                }
                return true;
            };
            Func<int, long, long> dfs = null;
            dfs = (vtx, c) =>
            {
                if (vtx == t) return c;
                foreach (var item in f[vtx])
                {
                    if (item.Value > 0 && level[vtx] < level[item.Key])
                    {
                        var flow = dfs(item.Key, Min(c, item.Value));
                        if (flow == 0) continue;
                        f[vtx][item.Key] -= flow;
                        f[item.Key][vtx] += flow;
                        return flow;
                    }
                }
                return 0;
            };
            var sum = 0L;
            while (reset() && level[t] > 0) for (long flow; (flow = dfs((int)s, long.MaxValue)) > 0;) sum += flow;
            for (var i = 0; i < path.Length; i++) foreach (var to in path[i]) f[i][to.Key] = to.Value - f[i][to.Key];
            return new FlowResult { maxflow = sum, fromToCost = f };
        }
    }
    class LIB_Dict<K, V> : Dictionary<K, V>
    {
        Func<K, V> d;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Dict(Func<K, V> _d) { d = _d; }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Dict() : this(_ => default(V)) { }
        new public V this[K i]
        {
            get
            {
                return TryGetValue(i, out var v) ? v : base[i] = d(i);
            }
            set
            {
                base[i] = value;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override int GetHashCode()
        {
            unchecked
            {
                var ret = 23;
                for (var e = GetEnumerator(); e.MoveNext();) ret = (ret * 37) ^ (e.Current.Key.GetHashCode() << 5 + e.Current.Key.GetHashCode()) ^ e.Current.Value.GetHashCode();
                return ret;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override bool Equals(object obj)
        {
            var o = (LIB_Dict<K, V>)obj;
            foreach (var kv in o)
            {
                if (!ContainsKey(kv.Key) || !this[kv.Key].Equals(kv.Value))
                    return false;
            }
            return o.Count == Count;
        }
    }
    class LIB_FastIO
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_FastIO() { str = Console.OpenStandardInput(); }
        readonly Stream str;
        readonly byte[] buf = new byte[1024];
        int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return isEof; }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        byte read()
        {
            if (isEof) throw new EndOfStreamException();
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        char Char()
        {
            byte b = 0;
            do b = read();
            while (b < 33 || 126 < b);
            return (char)b;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public long Long()
        {
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != '-' && (b < '0' || '9' < b));
            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';
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public double Double() { return double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
    class LIB_FastIODebug : LIB_FastIO
    {
        Queue<string> param = new Queue<string>();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        string NextString() { if (param.Count == 0) foreach (var item in Console.ReadLine().Split(' ')) param.Enqueue(item); return param.Dequeue(); }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_FastIODebug() { }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override string Scan() => NextString();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override long Long() => long.Parse(NextString());
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override double Double() => double.Parse(NextString());
    }
}


Measured memory_bytes: 37828