using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Reflection.Metadata;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;

namespace AtCoder
{
    public class Program
    {
        static void Main()
        {
            using var cin = new Scanner();
            var (n, m) = cin.Int2();
            var s = new string[n];
            for (int i = 0; i < n; i++)
            {
                s[i] = cin.Next();
            }

            int num = n * m + 2;
            int si = n * m;
            int ti = n * m + 1;
            var flow = MFGraph.Long(num);
            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    if (s[i][j] == '#')
                    {
                        continue;
                    }

                    int k = i * m + j;
                    if ((i + j) % 2 == 0)
                    {
                        flow.AddEdge(si, k, 1);
                        Helper.DoAt4(i, j, n, m, (ii, jj) =>
                        {
                            if (s[ii][jj] == '.')
                            {
                                int kk = ii * m + jj;
                                flow.AddEdge(k, kk, 1);
                            }
                        });
                    }
                    else
                    {
                        flow.AddEdge(k, ti, 1);
                    }
                }
            }

            long maxFlow = flow.Flow(si, ti);
            Console.WriteLine(maxFlow);

            var ans = new char[n][];
            for (int i = 0; i < n; i++)
            {
                ans[i] = new char[m];
            }

            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    ans[i][j] = s[i][j];
                }
            }

            var edges = flow.Edges();
            foreach (var e in edges)
            {
                if (e.From == si || e.To == ti || e.Flow == 0)
                {
                    continue;
                }

                int i0 = e.From / m;
                int j0 = e.From % m;
                int i1 = e.To / m;
                int j1 = e.To % m;

                if (i0 == i1 + 1)
                {
                    ans[i1][j1] = 'v';
                    ans[i0][j0] = '^';
                }
                else if (j0 == j1 + 1)
                {
                    ans[i1][j1] = '>';
                    ans[i0][j0] = '<';
                }
                else if (i0 == i1 - 1)
                {
                    ans[i0][j0] = 'v';
                    ans[i1][j1] = '^';
                }
                else
                {
                    ans[i0][j0] = '>';
                    ans[i1][j1] = '<';
                }
            }

            for (int i = 0; i < n; i++)
            {
                Console.WriteLine(new string(ans[i]));
            }
        }
    }
    public interface INumOperater<T> where T : struct
    {
        public T Zero { get; }
        public bool IsZero(T v);
        public T MaxValue { get; }
        T Add(T v1, T v2);
        T Sub(T v1, T v2);
        bool LessThan(T l, T r);
        bool LessThanEquals(T l, T r);
        bool GreaterThan(T l, T r);
        bool GreaterThanEquals(T l, T r);
    }
    public readonly struct IntOperater : INumOperater<int>
    {
        public int Zero => 0;
        public bool IsZero(int v) => v == 0;
        public int MaxValue => int.MaxValue;
        public int Add(int v1, int v2) => v1 + v2;
        public int Sub(int v1, int v2) => v1 - v2;
        public bool LessThan(int l, int r) => l < r;
        public bool LessThanEquals(int l, int r) => l <= r;
        public bool GreaterThan(int l, int r) => l > r;
        public bool GreaterThanEquals(int l, int r) => l >= r;
    }
    public readonly struct LongOperater : INumOperater<long>
    {
        public long Zero => 0;
        public bool IsZero(long v) => v == 0;
        public long MaxValue => long.MaxValue;
        public long Add(long v1, long v2) => v1 + v2;
        public long Sub(long v1, long v2) => v1 - v2;
        public bool LessThan(long l, long r) => l < r;
        public bool LessThanEquals(long l, long r) => l <= r;
        public bool GreaterThan(long l, long r) => l > r;
        public bool GreaterThanEquals(long l, long r) => l >= r;
    }
    public static class MFGraph
    {
        public static MFGraph<long, LongOperater> Long(int n) => new MFGraph<long, LongOperater>(n);
    }
    public class MFGraph<TValue, TOp>
        where TValue : struct
        where TOp : struct, INumOperater<TValue>
    {
        static TOp op = default;
        public MFGraph(int n)
        {
            _n = n;
            _g = new List<EdgeInternal>[n];
            for (int i = 0; i < n; i++)
            {
                _g[i] = new List<EdgeInternal>();
            }
            _pos = new List<(int first, int second)>();
        }

        public int AddEdge(int from, int to, TValue cap)
        {
            int m = _pos.Count;
            Debug.Assert(0 <= from && from < _n);
            Debug.Assert(0 <= to && to < _n);
            //Debug.Assert(0 <= cap);
            _pos.Add((from, _g[from].Count));
            _g[from].Add(new EdgeInternal(to, _g[to].Count, cap));
            _g[to].Add(new EdgeInternal(from, _g[from].Count - 1, default));
            return m;
        }

        public Edge GetEdge(int i)
        {
            int m = _pos.Count;
            Debug.Assert(0 <= i && i < m);
            var _e = _g[_pos[i].first][_pos[i].second];
            var _re = _g[_e.To][_e.Rev];
            return new Edge(_pos[i].first, _e.To, op.Add(_e.Cap, _re.Cap), _re.Cap);
        }

        public List<Edge> Edges()
        {
            int m = _pos.Count;
            var result = new List<Edge>();
            for (int i = 0; i < m; i++)
            {
                result.Add(GetEdge(i));
            }
            return result;
        }

        public void ChangeEdge(int i, TValue newCap, TValue newFlow)
        {
            int m = _pos.Count;
            Debug.Assert(0 <= i && i < m);
            //Debug.Assert(0 <= new_flow && new_flow <= new_cap);
            var _e = _g[_pos[i].first][_pos[i].second];
            var _re = _g[_e.To][_e.Rev];
            _e.Cap = op.Sub(newCap, newFlow);
            _re.Cap = newFlow;
        }

        public TValue Flow(int s, int t)
        {
            return Flow(s, t, op.MaxValue);
        }

        public TValue Flow(int s, int t, TValue flowLimit)
        {
            Debug.Assert(0 <= s && s < _n);
            Debug.Assert(0 <= t && t < _n);

            var level = new int[_n];
            var iter = new int[_n];
            var que = new Queue<int>();

            void Bfs()
            {
                for (int i = 0; i < _n; i++)
                {
                    level[i] = -1;
                }

                level[s] = 0;
                que.Clear();
                que.Enqueue(s);
                while (que.Count > 0)
                {
                    int v = que.Dequeue();
                    foreach (var e in _g[v])
                    {
                        if (op.IsZero(e.Cap) || level[e.To] >= 0) continue;
                        level[e.To] = level[v] + 1;
                        if (e.To == t) return;
                        que.Enqueue(e.To);
                    }
                }
            }

            TValue Dfs(int v, TValue up)
            {
                if (v == s) return up;
                var res = default(TValue);
                int level_v = level[v];
                for (int i = iter[v]; i < _g[v].Count; i++)
                {
                    EdgeInternal e = _g[v][i];
                    if (level_v <= level[e.To] || op.IsZero(_g[e.To][e.Rev].Cap)) continue;
                    var up1 = op.Sub(up, res);
                    var up2 = _g[e.To][e.Rev].Cap;
                    var d = Dfs(e.To, op.LessThan(up1, up2) ? up1 : up2);
                    if (op.LessThanEquals(d, op.Zero)) continue;
                    _g[v][i].Cap = op.Add(_g[v][i].Cap, d);
                    _g[e.To][e.Rev].Cap = op.Sub(_g[e.To][e.Rev].Cap, d);
                    res = op.Add(res, d);
                    if (res.Equals(up)) break;
                }

                return res;
            }

            TValue flow = default;
            while (op.LessThan(flow, flowLimit))
            {
                Bfs();
                if (level[t] == -1) break;
                for (int i = 0; i < _n; i++)
                {
                    iter[i] = 0;
                }
                while (op.LessThan(flow, flowLimit))
                {
                    var f = Dfs(t, op.Sub(flowLimit, flow));
                    if (op.IsZero(f)) break;
                    flow = op.Add(flow, f);
                }
            }
            return flow;
        }

        public bool[] MinCut(int s)
        {
            var visited = new bool[_n];
            var que = new Queue<int>();
            que.Enqueue(s);
            while (que.Count > 0)
            {
                int p = que.Dequeue();
                visited[p] = true;
                foreach (var e in _g[p])
                {
                    if (!op.IsZero(e.Cap) && !visited[e.To])
                    {
                        visited[e.To] = true;
                        que.Enqueue(e.To);
                    }
                }
            }

            return visited;
        }

        public struct Edge
        {
            public int From { get; set; }
            public int To { get; set; }
            public TValue Cap { get; set; }
            public TValue Flow { get; set; }
            public Edge(int from, int to, TValue cap, TValue flow)
            {
                From = from;
                To = to;
                Cap = cap;
                Flow = flow;
            }
        };

        private class EdgeInternal
        {
            public int To { get; set; }
            public int Rev { get; set; }
            public TValue Cap { get; set; }
            public EdgeInternal(int to, int rev, TValue cap)
            {
                To = to;
                Rev = rev;
                Cap = cap;
            }
        };

        private readonly int _n;
        private readonly List<(int first, int second)> _pos;
        private readonly List<EdgeInternal>[] _g;
    }

    public class HashMap<TKey, TValue> : Dictionary<TKey, TValue>
    {
        private readonly Func<TKey, TValue> initialzier_;
        public HashMap(Func<TKey, TValue> initialzier)
            : base()
        {
            initialzier_ = initialzier;
        }

        public HashMap(Func<TKey, TValue> initialzier, int capacity)
            : base(capacity)
        {
            initialzier_ = initialzier;
        }

        new public TValue this[TKey key]
        {
            get
            {
                if (ContainsKey(key) == false)
                {
                    base[key] = initialzier_(key);
                }

                return base[key];
            }

            set { base[key] = value; }
        }
    }

    public struct ModInt
    {
        public const long P = 1000000007;
        //public const long P = 998244353;

        public static ModInt Inverse(ModInt value) => Pow(value, P - 2);
        public static ModInt Pow(ModInt value, long k) => Pow(value.value_, k);
        public static ModInt Pow(long value, long k)
        {
            long ret = 1;
            for (k %= P - 1; k > 0; k >>= 1, value = value * value % P)
            {
                if ((k & 1) == 1)
                {
                    ret = ret * value % P;
                }
            }
            return new ModInt(ret);
        }

        private long value_;

        public ModInt(long value)
            => value_ = value;
        public ModInt(long value, bool mods)
        {
            if (mods)
            {
                value %= P;
                if (value < 0)
                {
                    value += P;
                }
            }

            value_ = value;
        }

        public static ModInt operator +(ModInt lhs, ModInt rhs)
        {
            lhs.value_ = (lhs.value_ + rhs.value_) % P;
            return lhs;
        }
        public static ModInt operator +(long lhs, ModInt rhs)
        {
            rhs.value_ = (lhs + rhs.value_) % P;
            return rhs;
        }
        public static ModInt operator +(ModInt lhs, long rhs)
        {
            lhs.value_ = (lhs.value_ + rhs) % P;
            return lhs;
        }

        public static ModInt operator -(ModInt lhs, ModInt rhs)
        {
            lhs.value_ = (P + lhs.value_ - rhs.value_) % P;
            return lhs;
        }
        public static ModInt operator -(long lhs, ModInt rhs)
        {
            rhs.value_ = (P + lhs - rhs.value_) % P;
            return rhs;
        }
        public static ModInt operator -(ModInt lhs, long rhs)
        {
            lhs.value_ = (P + lhs.value_ - rhs) % P;
            return lhs;
        }

        public static ModInt operator *(ModInt lhs, ModInt rhs)
        {
            lhs.value_ = lhs.value_ * rhs.value_ % P;
            return lhs;
        }
        public static ModInt operator *(long lhs, ModInt rhs)
        {
            rhs.value_ = lhs * rhs.value_ % P;
            return rhs;
        }
        public static ModInt operator *(ModInt lhs, long rhs)
        {
            lhs.value_ = lhs.value_ * rhs % P;
            return lhs;
        }

        public static ModInt operator /(ModInt lhs, ModInt rhs)
        {
            long exp = P - 2;
            while (exp > 0)
            {
                if (exp % 2 > 0)
                {
                    lhs *= rhs;
                }

                rhs *= rhs;
                exp /= 2;
            }

            return lhs;
        }

        public static implicit operator ModInt(long n) => new ModInt(n, true);
        public long ToLong() => value_;
        public override string ToString() => value_.ToString();
    }

    public static class Helper
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UpdateMin<T>(ref T target, T value) where T : IComparable<T>
            => target = target.CompareTo(value) > 0 ? value : target;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UpdateMin<T>(ref T target, T value, Action<T> onUpdated) where T : IComparable<T>
        {
            if (target.CompareTo(value) > 0)
            {
                target = value;
                onUpdated(value);
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UpdateMax<T>(ref T target, T value) where T : IComparable<T>
            => target = target.CompareTo(value) < 0 ? value : target;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UpdateMax<T>(ref T target, T value, Action<T> onUpdated) where T : IComparable<T>
        {
            if (target.CompareTo(value) < 0)
            {
                target = value;
                onUpdated(value);
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T[] Array<T>(int n, Func<int, T> init)
            => Enumerable.Range(0, n).Select(x => init(x)).ToArray();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static List<T> List<T>(int n, Func<int, T> init)
            => Enumerable.Range(0, n).Select(x => init(x)).ToList();

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T[,] Array2<T>(int n, int m, T init)
            where T : struct
        {
            var array = new T[n, m];
            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    array[i, j] = init;
                }
            }

            return array;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T[,] Array2<T>(int n, int m, Func<int, int, T> initializer)
        {
            var array = new T[n, m];
            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    array[i, j] = initializer(i, j);
                }
            }

            return array;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T[,,] Array3<T>(int n1, int n2, int n3, T init)
            where T : struct
        {
            var array = new T[n1, n2, n3];
            for (int i1 = 0; i1 < n1; i1++)
            {
                for (int i2 = 0; i2 < n2; i2++)
                {
                    for (int i3 = 0; i3 < n3; i3++)
                    {
                        array[i1, i2, i3] = init;
                    }
                }
            }

            return array;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T[,,,] Array4<T>(int n1, int n2, int n3, int n4, T init)
            where T : struct
        {
            var array = new T[n1, n2, n3, n4];
            for (int i1 = 0; i1 < n1; i1++)
            {
                for (int i2 = 0; i2 < n2; i2++)
                {
                    for (int i3 = 0; i3 < n3; i3++)
                    {
                        for (int i4 = 0; i4 < n4; i4++)
                        {
                            array[i1, i2, i3, i4] = init;
                        }
                    }
                }
            }

            return array;
        }

        private static readonly int[] delta4_ = { 1, 0, -1, 0, 1 };
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void DoAt4(int i, int j, int imax, int jmax, Action<int, int> action)
        {
            for (int dn = 0; dn < 4; dn++)
            {
                int d4i = i + delta4_[dn];
                int d4j = j + delta4_[dn + 1];
                if ((uint)d4i < (uint)imax && (uint)d4j < (uint)jmax)
                {
                    action(d4i, d4j);
                }
            }
        }

        private static readonly int[] delta8_ = { 1, 0, -1, 0, 1, 1, -1, -1, 1 };
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void DoAt8(int i, int j, int imax, int jmax, Action<int, int> action)
        {
            for (int dn = 0; dn < 8; dn++)
            {
                int d8i = i + delta8_[dn];
                int d8j = j + delta8_[dn + 1];
                if ((uint)d8i < (uint)imax && (uint)d8j < (uint)jmax)
                {
                    action(d8i, d8j);
                }
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void ForEachSubBit(int bit, Action<int> action)
        {
            for (int sub = bit; sub >= 0; sub--)
            {
                sub &= bit;
                action(sub);
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static string Reverse(string src)
        {
            var chars = src.ToCharArray();
            for (int i = 0, j = chars.Length - 1; i < j; i++, j--)
            {
                var tmp = chars[i];
                chars[i] = chars[j];
                chars[j] = tmp;
            }
            return new string(chars);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static string Join<T>(this IEnumerable<T> values, string separator = "")
            => string.Join(separator, values);
    }

    public class Scanner : IDisposable
    {
        private const int BUFFER_SIZE = 1024;
        private const int ASCII_CHAR_BEGIN = 33;
        private const int ASCII_CHAR_END = 126;
        private readonly string filePath_;
        private readonly Stream stream_;
        private readonly byte[] buf_ = new byte[BUFFER_SIZE];
        private int length_ = 0;
        private int index_ = 0;
        private bool isEof_ = false;

        public Scanner(string file = "")
        {
            if (string.IsNullOrWhiteSpace(file))
            {
                stream_ = Console.OpenStandardInput();
            }
            else
            {
                filePath_ = file;
                stream_ = new FileStream(file, FileMode.Open);
            }

            Console.SetOut(new StreamWriter(Console.OpenStandardOutput())
            {
                AutoFlush = false
            });
        }

        public void Dispose()
        {
            Console.Out.Flush();
            stream_.Dispose();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public char Char()
        {
            byte b;
            do
            {
                b = Read();
            } while (b < ASCII_CHAR_BEGIN || ASCII_CHAR_END < b);

            return (char)b;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public string Next()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= ASCII_CHAR_BEGIN && b <= ASCII_CHAR_END; b = (char)Read())
            {
                sb.Append(b);
            }

            return sb.ToString();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int Int() => (int)Long();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int Int(int offset) => Int() + offset;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (int, int) Int2(int offset = 0)
            => (Int(offset), Int(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (int, int, int) Int3(int offset = 0)
            => (Int(offset), Int(offset), Int(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (int, int, int, int) Int4(int offset = 0)
            => (Int(offset), Int(offset), Int(offset), Int(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int[] ArrayInt(int length, int offset = 0)
        {
            int[] Array = new int[length];
            for (int i = 0; i < length; i++)
            {
                Array[i] = Int(offset);
            }
            return Array;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public long Long()
        {
            long ret = 0;
            byte b;
            bool 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)]
        public long Long(long offset) => Long() + offset;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (long, long) Long2(long offset = 0)
            => (Long(offset), Long(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (long, long, long) Long3(long offset = 0)
            => (Long(offset), Long(offset), Long(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (long, long, long, long) Long4(long offset = 0)
            => (Long(offset), Long(offset), Long(offset), Long(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public long[] ArrayLong(int length, long offset = 0)
        {
            long[] Array = new long[length];
            for (int i = 0; i < length; i++)
            {
                Array[i] = Long(offset);
            }
            return Array;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public double Double() => double.Parse(Next(), CultureInfo.InvariantCulture);
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public double Double(double offset) => Double() + offset;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (double, double) Double2(double offset = 0)
            => (Double(offset), Double(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (double, double, double) Double3(double offset = 0)
            => (Double(offset), Double(offset), Double(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public (double, double, double, double) Double4(double offset = 0)
            => (Double(offset), Double(offset), Double(offset), Double(offset));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public double[] ArrayDouble(int length, double offset = 0)
        {
            double[] Array = new double[length];
            for (int i = 0; i < length; i++)
            {
                Array[i] = Double(offset);
            }
            return Array;
        }

        private byte Read()
        {
            if (isEof_)
            {
                throw new EndOfStreamException();
            }

            if (index_ >= length_)
            {
                index_ = 0;
                if ((length_ = stream_.Read(buf_, 0, BUFFER_SIZE)) <= 0)
                {
                    isEof_ = true;
                    return 0;
                }
            }

            return buf_[index_++];
        }

        public void Save(string text)
        {
            if (string.IsNullOrWhiteSpace(filePath_))
            {
                return;
            }

            File.WriteAllText(filePath_ + "_output.txt", text);
        }
    }
}


Measured memory_bytes: 31200