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 ProblemA
    {
        static bool SAIKI = false;
        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_MaxFlow(N * M + 2);
            var startVtx = N * M;
            var goalVtx = startVtx + 1;
            var idx = new int[N, M];
            for (var i = 0; i < N; i++)
            {
                for (var j = 0; j < M; j++)
                {
                    var vtx = i * M + j;
                    if (S[i][j] == '#') continue;
                    if ((i + j) % 2 == 0)
                    {
                        flow.AddEdge(startVtx, vtx, 1);
                        if (i > 0 && S[i - 1][j] != '#') idx[i, j] = flow.AddEdge(vtx, vtx - M, 1);
                        if (j > 0 && S[i][j - 1] != '#') idx[i, j] = flow.AddEdge(vtx, vtx - 1, 1);
                        if (i < N - 1 && S[i + 1][j] != '#') idx[i, j] = flow.AddEdge(vtx, vtx + M, 1);
                        if (j < M - 1 && S[i][j + 1] != '#') idx[i, j] = flow.AddEdge(vtx, vtx + 1, 1);
                    }
                    else flow.AddEdge(vtx, goalVtx, 1);
                }
            }
            var res = flow.Flow(startVtx, goalVtx);
            Console.WriteLine(res);
            var ans = new char[N, M];
            for (var i = 0; i < N; i++)
            {
                for (var j = 0; j < M; j++)
                {
                    ans[i, j] = S[i][j];
                }
            }
            foreach (var item in flow.GetAllEdge())
            {
                if (item.from != startVtx && item.to != goalVtx && item.flow == 1)
                {
                    var fx = item.from / M;
                    var fy = item.from % M;
                    var tx = item.to / M;
                    var ty = item.to % M;
                    if (fx > tx)
                    {
                        ans[tx, ty] = 'v';
                        ans[fx, fy] = '^';
                    }
                    else if (fx < tx)
                    {
                        ans[fx, fy] = 'v';
                        ans[tx, ty] = '^';
                    }
                    else if (fy < ty)
                    {
                        ans[fx, fy] = '>';
                        ans[tx, ty] = '<';
                    }
                    else
                    {
                        ans[fx, fy] = '<';
                        ans[tx, ty] = '>';
                    }
                }
            }
            for (var i = 0; i < N; i++)
            {
                for (var j = 0; j < M; j++)
                {
                    Console.Write(ans[i, j]);
                }
                Console.WriteLine();
            }
        }
        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_MaxFlow
    {
        public struct Edge
        {
            public int from;
            public int to;
            public long cap;
            public long flow;
        }
        const int SHIFT_SIZE = 30;
        const int MASK = 1073741823;
        List<ulong> pos;
        List<int>[] gTo;
        List<int>[] gRev;
        List<long>[] gCap;
        int N;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_MaxFlow(long n)
        {
            N = (int)n;
            pos = new List<ulong>();
            gTo = new List<int>[n];
            gRev = new List<int>[n];
            gCap = new List<long>[n];
            for (var i = 0; i < n; i++)
            {
                gTo[i] = new List<int>();
                gRev[i] = new List<int>();
                gCap[i] = new List<long>();
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int AddEdge(long from, long to, long cap)
        {
            var ret = pos.Count;
            pos.Add(((ulong)from << SHIFT_SIZE) | (uint)gTo[from].Count);
            gTo[from].Add((int)to);
            gRev[from].Add(gRev[to].Count);
            gCap[from].Add(cap);
            gTo[to].Add((int)from);
            gRev[to].Add(gRev[from].Count - 1);
            gCap[to].Add(0);
            return ret;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public Edge GetEdge(long i)
        {
            var idx = (int)i;
            var idxf = pos[idx] >> SHIFT_SIZE;
            var idxt = (int)(pos[idx] & MASK);
            var eTo = gTo[idxf][idxt];
            var eRev = gRev[idxf][idxt];
            var reCap = gCap[eTo][eRev];
            return new Edge { from = (int)(pos[idx] >> SHIFT_SIZE), to = eTo, cap = gCap[idxf][idxt] + reCap, flow = reCap };
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public Edge[] GetAllEdge()
        {
            var res = new Edge[pos.Count];
            for (var i = 0; i < res.Length; ++i) res[i] = GetEdge(i);
            return res;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void ChangeEdge(long i, long newCap, long newFlow)
        {
            var idx = (int)i;
            var idxf = pos[idx] >> SHIFT_SIZE;
            var idxt = (int)(pos[idx] & MASK);
            gCap[idxf][idxt] = newCap - newFlow;
            gCap[gTo[idxf][idxt]][gRev[idxf][idxt]] = newFlow;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public long Flow(long s, long t) => Flow(s, t, long.MaxValue >> 2);
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public long Flow(long s, long t, long flowLimit)
        {
            var level = new int[N];
            var iter = new int[N];
            var que = new Queue<int>();
            Func<int, long, long> dfs = null;
            dfs = (v, up) =>
            {
                var res = 0L;
                var levelv = level[v];
                var gToV = gTo[v];
                var gCapV = gCap[v];
                var gRevV = gRev[v];
                for (; iter[v] < gToV.Count; ++iter[v])
                {
                    var gToVi = gToV[iter[v]];
                    var gRevVi = gRevV[iter[v]];
                    var gcap = gCap[gToVi][gRevVi];
                    if (levelv <= level[gToVi] || gcap == 0) continue;
                    var param = Math.Min(up - res, gcap);
                    var d = gToVi == s ? param : dfs(gToVi, param);
                    if (d <= 0) continue;
                    gCapV[iter[v]] += d;
                    gCap[gToVi][gRevVi] -= d;
                    res += d;
                    if (res == up) break;
                }
                return res;
            };
            var flow = 0L;
            while (flow < flowLimit)
            {
                for (var i = 0; i < level.Length; ++i) level[i] = -1;
                level[s] = 0;
                que.Enqueue((int)s);
                while (que.Count > 0)
                {
                    var v = que.Dequeue();
                    var gToV = gTo[v];
                    var gCapV = gCap[v];
                    var levelv = level[v] + 1;
                    for (var i = 0; i < gToV.Count; ++i)
                    {
                        var gToVi = gToV[i];
                        if (gCapV[i] == 0 || level[gToVi] >= 0) continue;
                        level[gToVi] = levelv;
                        if (gToVi == t)
                        {
                            que.Clear();
                            break;
                        }
                        que.Enqueue(gToVi);
                    }
                }
                if (level[t] == -1) break;
                iter = new int[N];
                while (flow < flowLimit)
                {
                    var f = t == s ? (flowLimit - flow) : dfs((int)t, flowLimit - flow);
                    if (f == 0) break;
                    flow += f;
                }
            }
            return flow;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool[] MinCut(long s)
        {
            var visited = new bool[N];
            var que = new Queue<int>();
            que.Enqueue((int)s);
            while (que.Count > 0)
            {
                var p = que.Dequeue();
                visited[p] = true;
                var gToP = gTo[p];
                var gCapP = gCap[p];
                for (var i = 0; i < gToP.Count; ++i)
                {
                    var gToPi = gToP[i];
                    if (gCapP[i] > 0 && !visited[gToPi])
                    {
                        visited[gToPi] = true;
                        que.Enqueue(gToPi);
                    }
                }
            }
            return visited;
        }
    }
    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: 30756