using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Text;
using System.Linq;

using E = System.Linq.Enumerable;
using Weight = System.Int32;
using System.Threading;

internal partial class Solver {
    public void Run() {
        var h = ni();
        var w = ni();
        var s = ns(h).Select(x => new StringBuilder(x)).ToArray();
        var dinic = new Dinic(h * w + 2);
        int source = h * w;
        int sink = source + 1;

        int toId(int row, int col) => row * w + col;
        (int Row, int Col) FromId(int id) => (id / w, id % w);
        void AddEdge(int r1, int c1, int r2, int c2) {
            if ((r1 + c1) % 2 == 1) AddEdge(r2, c2, r1, c1);
            else {
                dinic.AddEdge(toId(r1, c1), toId(r2, c2), 1);
            }
        }

        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                if ((i + j) % 2 == 0) dinic.AddEdge(source, toId(i, j), 1);
                else dinic.AddEdge(toId(i, j), sink, 1);
            }
        }

        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                if (s[i][j] == '#') continue;
                if (i + 1 < h && s[i + 1][j] == '.') {
                    AddEdge(i, j, i + 1, j);
                }
                if (j + 1 < w && s[i][j + 1] == '.') {
                    AddEdge(i, j, i, j + 1);
                }
            }
        }
        cout.WriteLine(dinic.Run(source, sink));

        foreach (var edge in dinic.GetEdges()) {
            if (edge.From >= source) continue;
            if (edge.To >= source) continue;
            if (edge.Flow == 0) continue;
            //new { edge.From, edge.To, edge.Flow }.TextDump();
            var (row1, col1) = FromId(edge.From);
            var (row2, col2) = FromId(edge.To);
            if ((row1 + col1) % 2 == 1) continue;
            if ((row2 + col2) % 2 == 0) continue;
            if (row1 == row2) {
                if (col1 < col2) {
                    s[row1][col1] = '>';
                    s[row2][col2] = '<';
                } else {
                    s[row1][col1] = '<';
                    s[row2][col2] = '>';
                }
            } else {
                if (row1 < row2) {
                    s[row1][col1] = 'v';
                    s[row2][col2] = '^';
                } else {
                    s[row1][col1] = '^';
                    s[row2][col2] = 'v';
                }
            }
        }

        for (int i = 0; i < h; i++) {
            cout.WriteLine(s[i]);
        }
    }
}

public class Dinic {
    public readonly int N;
    private readonly List<List<Edge>> adjacents;
    private readonly int[] levels;
    private readonly bool[] used;

    public class Edge {
        public int From, To;
        public Weight Flow, Capacity;
        public Edge Reverse;
        public Edge(int from, int to, Weight capacity, Weight flow = 0) {
            From = from;
            To = to;
            Flow = flow;
            Capacity = capacity;
        }
        public Weight Residue { get { return Capacity - Flow; } }
    }

    public Dinic(int n) {
        N = n;
        adjacents = new List<List<Edge>>();
        levels = new int[N];
        used = new bool[N];
        for (int i = 0; i < N; i++) {
            adjacents.Add(new List<Edge>());
        }
    }

    public void AddEdge(int from, int to, Weight capacity) {
        var e1 = new Edge(from, to, capacity);
        var e2 = new Edge(to, from, 0);
        e1.Reverse = e2;
        e2.Reverse = e1;
        adjacents[from].Add(e1);
        adjacents[to].Add(e2);
    }

    public IEnumerable<Edge> GetEdges() {
        return adjacents.SelectMany(a => a);
    }

    private bool Levelize(int s, int t) {
        for (int i = 0; i < N; i++) {
            levels[i] = -1;
        }
        var queue = new Queue<int>();
        levels[s] = 0;
        queue.Enqueue(s);
        while (queue.Count > 0) {
            int pos = queue.Dequeue();
            foreach (var edge in adjacents[pos]) {
                if (levels[edge.To] == -1 && edge.Residue > 0) {
                    levels[edge.To] = levels[pos] + 1;
                    queue.Enqueue(edge.To);
                }
            }
        }
        return levels[t] != -1;
    }

    private Weight Augment(int pos, int end, Weight cur) {
        int flowOut = 0;
        foreach (var edge in adjacents[pos]) {
            if (levels[edge.To] == levels[pos] + 1) {
                int f = Math.Min(cur - flowOut, edge.Residue);
                if (f <= 0) {
                    continue;
                }

                if ((edge.To == end) || (!used[edge.To] && (f = Augment(edge.To, end, f)) > 0)) {
                    edge.Flow += f;
                    edge.Reverse.Flow -= f;
                    flowOut += f;
                    if (cur - flowOut == 0) {
                        return flowOut;
                    }
                }
            }
        }
        used[pos] = flowOut == 0;
        return flowOut;
    }

    public Weight Run(int source, int sink) {
        int totalFlow = 0;

        while (Levelize(source, sink)) {
            Array.Clear(used, 0, used.Length);
            totalFlow += Augment(source, sink, Weight.MaxValue);
        }

        return totalFlow;
    }
}
// PREWRITEN CODE BEGINS FROM HERE

static public class StringExtensions {
    static public string JoinToString<T>(this IEnumerable<T> source, string separator = " ") {
        return string.Join(separator, source);
    }
}

internal partial class Solver : Scanner {
    static readonly int? StackSizeInMebiByte = null; //50;
    public static void StartAndJoin(Action action, int maxStackSize) {
        var thread = new Thread(new ThreadStart(action), maxStackSize);
        thread.Start();
        thread.Join();
    }

    public static void Main() {
#if LOCAL
        byte[] inputBuffer = new byte[1000000];
        var inputStream = Console.OpenStandardInput(inputBuffer.Length);
        using (var reader = new StreamReader(inputStream, Console.InputEncoding, false, inputBuffer.Length)) {
            Console.SetIn(reader);
            new Solver(Console.In, Console.Out).Run();
        }
#else
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        if (StackSizeInMebiByte.HasValue) {
            StartAndJoin(() => new Solver(Console.In, Console.Out).Run(), StackSizeInMebiByte.Value * 1024 * 1024);
        } else {
            new Solver(Console.In, Console.Out).Run();
        }
        Console.Out.Flush();
#endif
    }

#pragma warning disable IDE0052
    private readonly TextReader cin;
    private readonly TextWriter cout;
    private readonly TextWriter cerr;
#pragma warning restore IDE0052

    public Solver(TextReader reader, TextWriter writer)
        : base(reader) {
        cin = reader;
        cout = writer;
        cerr = Console.Error;
    }

    public Solver(string input, TextWriter writer)
        : this(new StringReader(input), writer) {
    }

#pragma warning disable IDE1006
#pragma warning disable IDE0051
    private int ni() { return NextInt(); }
    private int[] ni(int n) { return NextIntArray(n); }
    private long nl() { return NextLong(); }
    private long[] nl(int n) { return NextLongArray(n); }
    private double nd() { return NextDouble(); }
    private double[] nd(int n) { return NextDoubleArray(n); }
    private string ns() { return Next(); }
    private string[] ns(int n) { return NextArray(n); }
#pragma warning restore IDE1006
#pragma warning restore IDE0051
}

#if DEBUG
internal static class LinqPadExtension {
    public static string TextDump<T>(this T obj) {
        if (obj is IEnumerable) return (obj as IEnumerable).Cast<object>().JoinToString().Dump();
        else return obj.ToString().Dump();
    }
    public static T Dump<T>(this T obj) {
        return LINQPad.Extensions.Dump(obj);
    }
}
#endif

public class Scanner {
    private readonly TextReader Reader;
    private readonly CultureInfo ci = CultureInfo.InvariantCulture;

    private readonly char[] buffer = new char[2 * 1024];
    private int cursor = 0, length = 0;
    private string Token;
    private readonly StringBuilder sb = new StringBuilder(1024);

    public Scanner()
        : this(Console.In) {
    }

    public Scanner(TextReader reader) {
        Reader = reader;
    }

    public int NextInt() { return checked((int)NextLong()); }
    public long NextLong() {
        var s = Next();
        long r = 0;
        int i = 0;
        bool negative = false;
        if (s[i] == '-') {
            negative = true;
            i++;
        }
        for (; i < s.Length; i++) {
            r = r * 10 + (s[i] - '0');
#if DEBUG
            if (!char.IsDigit(s[i])) throw new FormatException();
#endif
        }
        return negative ? -r : r;
    }
    public double NextDouble() { return double.Parse(Next(), ci); }
    public string[] NextArray(int size) {
        string[] array = new string[size];
        for (int i = 0; i < size; i++) {
            array[i] = Next();
        }

        return array;
    }
    public int[] NextIntArray(int size) {
        int[] array = new int[size];
        for (int i = 0; i < size; i++) {
            array[i] = NextInt();
        }

        return array;
    }

    public long[] NextLongArray(int size) {
        long[] array = new long[size];
        for (int i = 0; i < size; i++) {
            array[i] = NextLong();
        }

        return array;
    }

    public double[] NextDoubleArray(int size) {
        double[] array = new double[size];
        for (int i = 0; i < size; i++) {
            array[i] = NextDouble();
        }

        return array;
    }

    public string Next() {
        if (Token == null) {
            if (!StockToken()) {
                throw new Exception();
            }
        }
        var token = Token;
        Token = null;
        return token;
    }

    public bool HasNext() {
        if (Token != null) {
            return true;
        }

        return StockToken();
    }

    private bool StockToken() {
        while (true) {
            sb.Clear();
            while (true) {
                if (cursor >= length) {
                    cursor = 0;
                    if ((length = Reader.Read(buffer, 0, buffer.Length)) <= 0) {
                        break;
                    }
                }
                var c = buffer[cursor++];
                if (33 <= c && c <= 126) {
                    sb.Append(c);
                } else {
                    if (sb.Length > 0) break;
                }
            }

            if (sb.Length > 0) {
                Token = sb.ToString();
                return true;
            }

            return false;
        }
    }
}

Measured memory_bytes: 32172