#include <bits/stdc++.h>
//#include "bits/stdc++.h"
#include <atcoder/all>

using namespace std;
using namespace atcoder;
typedef long long ll;


#include "boost/multiprecision/cpp_int.hpp"
#include "boost/multiprecision/cpp_dec_float.hpp"
namespace mp = boost::multiprecision;
typedef mp::cpp_int LL;
typedef mp::number<mp::cpp_dec_float<1024>> DD;// 仮数部が1024ビットの浮動小数点数型(TLEしたら小さくする)

 
typedef long double dd;
#define i_7 (ll)(1E9+7)
//#define i_7 998244353
#define i_5 i_7-2
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    return c+i_7;
}
typedef pair<ll,ll> l_l;
typedef pair<dd,dd> d_d;
ll inf=(ll)1E16;
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define rrep(i,r,l) for(ll i=r;i>=l;i--)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}
void Max(ll &pos,ll val){pos=max(pos,val);}//Max(dp[n],dp[n-1]);
void Min(ll &pos,ll val){pos=min(pos,val);}
void Add(ll &pos,ll val){pos=mod(pos+val);}
dd EPS=1E-12;
#define fastio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fi first
#define se second
//#define endl "\n"  //インタラクティブで消す！！！！！！！！！！！！！！！！！！！！！
#define SORT(v) sort(v.begin(),v.end())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
#define POSL(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define POSU(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
template<class T,class S>
inline bool chmax(T &a, S b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
template<class T,class S>
inline bool chmin(T &a, S b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}

void mod_print(ll k){
    ll P=50000;
    rep(y,1,P){
        ll x=mod(y*k);
        
        if(abs(x)<=P||x+P>=i_7){
            if(x+P>=i_7){
                x-=i_7;
            }
            cout<<x<<"/"<<y<<endl;
            //cout<<setprecision(5)<<(dd)x/(dd)y;
            return;
        }
    }
    cout<<"nun"<<endl;
}
#define all(c) c.begin(),c.end()
typedef vector<ll> vl;
//////////////////////////

ll dx[4]={1,0,-1,0};
ll dy[4]={0,1,0,-1};
ll n,m;
bool valid(ll x,ll y){
    if(0<=x&&x<=n-1&&0<=y&&y<=m-1)return true;
    return false;
}
ll num(ll x,ll y){
    return x*m+y;
}
int main(){fastio
   cin>>n>>m;
    string s[n];rep(i,0,n-1)cin>>s[i];
    mf_graph<ll> g(n*m+2);
    ll A=n*m,B=n*m+1;
    rep(i,0,n-1){
        rep(j,0,m-1){
            if(s[i][j]=='#')continue;
            ll x=num(i,j);
            if((i+j)%2==0){
                g.add_edge(A,x,1);
            }else{
                g.add_edge(x,B,1);
            }
        }
    }
    rep(i,0,n-1){
        rep(j,0,m-1){
            if((i+j)%2==1)continue;
            rep(z,0,3){
                ll nx=i+dx[z];
                ll ny=j+dy[z];
                if(valid(nx,ny)){
                    g.add_edge(num(i,j),num(nx,ny),1);
                }
            }
        }
    }
    cout<<g.flow(A,B)<<endl;
    vector<mf_graph<ll>::edge>v=g.edges();
    
    /*for(auto x:v){
        cout<<x.from<<"→"<<x.to<<":"<<x.cap<<" "<<x.flow<<endl;
    }*/
    for(auto e:v){
        ll x=e.from,y=e.to;
        if(x>=n*m||y>=n*m)continue;
        if(e.flow==0)continue;
        ll i0=x/m,i1=x%m;
        ll j0=y/m,j1=y%m;
        //cout<<x<<" "<<y<<endl;
       // cout<<i0<<" "<<i1<<"   "<<j0<<" "<<j1<<endl;
        if(i0>j0||i1>j1){
            swap(i0,j0);
            swap(i1,j1);
        }
        if(i0==j0){
            s[i0][i1]='>';
            s[j0][j1]='<';
        }else{
            s[i0][i1]='v';
            s[j0][j1]='^';
        }
    }
    rep(i,0,n-1)cout<<s[i]<<endl;
    
    return 0;
}


Measured memory_bytes: 6328