using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
static class Program{
	const int mod=(int)1e9+7;
	const double eps=1e-11;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.Ia;
		var h=new int[s[0]][];
		int k=2;
		var ca=new char[s[0]][];
		for(int i = 0;i<s[0];i++) {
			ca[i]=sc.S.ToCharArray();
			h[i]=new int[s[1]];
			for(int j = 0;j<s[1];j++) {
				if(ca[i][j]=='.'){h[i][j]=k++;}
			}
		}
		var g=new (int,int)[k];
		var fl=new Mfp(k);
		for(int i = 0,l=2;i<s[0];i++) {
			for(int j = 0;j<s[1];j++) {
				if(h[i][j]!=0&&((i+j)&1)==0){
					fl.Edge(0,h[i][j],1);
					if(i>0&&h[i-1][j]!=0){fl.Edge(h[i][j],h[i-1][j],1);}
					if(j>0&&h[i][j-1]!=0){fl.Edge(h[i][j],h[i][j-1],1);}
					if(i<s[0]-1&&h[i+1][j]!=0){fl.Edge(h[i][j],h[i+1][j],1);}
					if(j<s[1]-1&&h[i][j+1]!=0){fl.Edge(h[i][j],h[i][j+1],1);}
					g[l++]=(i,j);
				}
				else if(h[i][j]!=0&&((i+j)&1)==1){
					fl.Edge(h[i][j],1,1);
					g[l++]=(i,j);
				}
			}
		}
		StringBuilder sb=new StringBuilder();
		sb.Append(fl.Dinic(0,1)+"\n");
		fl.Kc((v1,v2,a)=>{
			if(v1==0||v2==1){return;}
			if(g[v1].Item1==g[v2].Item1){
				if(g[v1].Item2>g[v2].Item2){
					ca[g[v1].Item1][g[v1].Item2]='<';
					ca[g[v2].Item1][g[v2].Item2]='>';
				}
				else{
					ca[g[v1].Item1][g[v1].Item2]='>';
					ca[g[v2].Item1][g[v2].Item2]='<';
				}
			}
			else{
				if(g[v1].Item1>g[v2].Item1){
					ca[g[v1].Item1][g[v1].Item2]='^';
					ca[g[v2].Item1][g[v2].Item2]='v';
				}
				else{
					ca[g[v1].Item1][g[v1].Item2]='v';
					ca[g[v2].Item1][g[v2].Item2]='^';
				}
			}
		});
		for(int i = 0;i<s[0];i++) {sb.Append(string.Join("",ca[i])+"\n");}
		Console.Write(sb);
	}
}
public class Mfp{
	public List<int>[] li;
	private Dictionary<int,(int,int)>[] h;
	private bool[] b;
	private int[] l;
	private int n,ans,go;
	private const int inf=int.MaxValue;
	public Mfp(int n){
		this.n=n;
		li=new List<int>[n];
		h=new Dictionary<int,(int,int)>[n+1];
		for(int i=0;i<n;i++){
			li[i]=new List<int>();
			h[i]=new Dictionary<int,(int,int)>();
		}
	}
	public void Edge(int a,int b,int c){
		if(a==b){return;}
		if(!h[a].ContainsKey(b)){
			li[a].Add(b);
			li[b].Add(a);
			h[a].Add(b,(c,c));
			h[b].Add(a,(0,0));
		}
		else{
			var p=h[a][b].Item1;
			h[a][b]=(c+p,c+p);
		}
	}
	public int Dinic(int st,int go){
		this.go=st;
		ans=0;
		int z=1;
		while(z>0){
			l=new int[n];
			var qu=new Queue<ValueTuple<int,int>>();
			qu.Enqueue(ValueTuple.Create(st,1));
			l[st]=1;
			while(qu.Count>0){
				var e=qu.Dequeue();
				for(int i=0;i<li[e.Item1].Count;i++){
					if(l[li[e.Item1][i]]==0&&h[e.Item1][li[e.Item1][i]].Item1!=0){
						l[li[e.Item1][i]]=e.Item2+1;
						qu.Enqueue(ValueTuple.Create(li[e.Item1][i],e.Item2+1));
					}
				}
				if(e.Item1==go){break;}
			}
			b=new bool[n];
			z=Fu3(go,inf);
			ans+=z;
		}
		return ans;
	}
	private int Fu3(int a,int p){
		if(a==go){return p;}
		int u=0;
		for(int i=0;i<li[a].Count&&p>u;i++){
			if(!b[li[a][i]]&&l[li[a][i]]<l[a]&&h[li[a][i]][a].Item1!=0){
				int z=Fu3(li[a][i],Min(p-u,h[li[a][i]][a].Item1));
				var e=h[li[a][i]][a];
				h[li[a][i]][a]=(e.Item1-z,e.Item2);
				e=h[a][li[a][i]];
				h[a][li[a][i]]=(e.Item1+z,e.Item2);
				u+=z;
			}
		}
		if(u==0){b[a]=true;}
		return u;
	}
	public int Ff(int st,int go){
		this.go=go;
		ans=0;
		int z=1;
		while(z>0){
			b=new bool[n];
			z=Fu2(st,inf);
			ans+=z;
		}
		return ans;
	}
	private int Fu2(int a,int p){
		if(a==go){return p;}
		int u=0;
		b[a]=true;
		for(int i=0;i<li[a].Count&&p>u;i++){
			if(!b[li[a][i]]&&h[a][li[a][i]].Item1!=0){
				int z=Fu2(li[a][i],Min(p-u,h[a][li[a][i]].Item1));
				var e=h[a][li[a][i]];
				h[a][li[a][i]]=(e.Item1-z,e.Item2);
				e=h[li[a][i]][a];
				h[li[a][i]][a]=(e.Item1+z,e.Item2);
				u+=z;
			}
		}
		if(u!=0){b[a]=false;}
		return u;
	}
	public void Vc(int s,Action<int> f){
		b=new bool[n];
		Fu4(s,0,f);
		for(int i=0;i<li[s].Count;i++){
			if(h[s][li[s][i]].Item1==0&&!b[li[s][i]]){f(li[s][i]);}
		}
	}
	private void Fu4(int a,int p,Action<int> f){
		b[a]=true;
		if((p&1)==0&&p!=0){f(a);}
		for(int i=0;i<li[a].Count;i++){
			if(h[a][li[a][i]].Item1!=0&&!b[li[a][i]]){Fu4(li[a][i],p+1,f);}
		}
	}
	public void Kc(Action<int,int,int> f){
		for(int i = 0;i<li.Length;i++) {
			foreach(var e in h[i]){
				if(e.Value.Item1<e.Value.Item2){f(i,e.Key,e.Value.Item2-e.Value.Item1);}
			}
		}
	}
}
public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),int.Parse);}
	public int[] Ia3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),long.Parse);}
	public long[] La3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<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;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}

Measured memory_bytes: 35332