#include <atcoder/all>
#include <bits/stdc++.h>
#define int long long
#define sint signed
#define endl "\n" // fflush(stdout);
#define ALL(v) (v).begin(),(v).end()
#define Vi vector<int>
#define VVi vector<Vi>
#define VVVi vector<VVi>
#define Vm vector<mint>
#define Vs vector<string>
#define Vd vector<double>
#define Vc vector<char>
#define Pii pair<int,int>
#define Pdd pair<double,double>
#define VPii vector<Pii>
#define Tiii tuple<int,int,int>
#define VTiii vector<Tiii>
#define PQi priority_queue<int>
#define PQir priority_queue<int,vector<int>,greater<int>>
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define itos to_string
#define stoi stoll
#define FI first
#define SE second
#define cYES cout<<"YES"<<endl
#define cNO cout<<"NO"<<endl
#define cYes cout<<"Yes"<<endl
#define cNo cout<<"No"<<endl
#define cyes cout<<"yes"<<endl
#define cno cout<<"no"<<endl
#define sortr(v) sort(v,greater<>())
#define rep(i,a,b) for(int i=a;i<b;i++)
#define repeq(i,a,b) for(int i=a;i<=b;i++)
#define repreq(i,a,b) for(int i=a;i>=b;i--)
#define dem(a,b) ((a+b-1)/(b))
#define INF 3000000000000000000 // 3.0*10^18
#define MAX LLONG_MAX
#define PI acos(-1.0L)

using namespace std;
using namespace atcoder;

/* debug */
template <typename T> // vector
ostream& operator<<(ostream& os,const vector<T> &V){int N=V.size();
if(N==0){os<<'.';return os;}rep(i,0,N-1){os<<V[i]<<' ';}os<<V[N-1];return os;}
template <typename T> // vector vector
ostream& operator<<(ostream& os,const vector<vector<T>> &V){
int N=V.size();rep(i,0,N-1)cout<<V[i]<<endl;cout<<V[N-1];return os;}
template <typename T,typename S> // pair
ostream& operator<<(ostream& os, pair<T,S> const&P){os<<P.FI<<' '<<P.SE;return os;}
template <typename T> // set
ostream& operator<<(ostream& os,set<T> &S){auto it=S.begin();while(it!=S.end()){
os<<*it;if(next(it,1)!=S.end())os<<' ';it++;};return os;}
template <typename T> // deque
ostream& operator<<(ostream& os, deque<T> &q){for(auto it=q.begin();it<q.end();it++){
os<<*it;if(it+1!=q.end())os<<" ";}return os;}

/* useful */
template<typename T>void Vin(vector<T> &v){int n=v.size();rep(i,0,n)cin>>v[i];}
int scomb(int n, int r){if(r<0||r>n)return 0;if((n-r)<r)r=n-r; // nCr
int a=1;for(int i=n;i>n-r;--i){a=a*i;}for(int i=1;i<r+1;++i){a=a/i;}return a;}
Vi vis(Vi &v){Vi S(v.size()+1);rep(i,1,S.size())S[i]+=v[i-1]+S[i-1];return S;}
int digit_sum(int n){int ret=0; while(n>0){ret+=n%10;n/=10;}return ret;}
int digit(int k,int i){string s = itos(k);return s[s.size()-i]-'0';} // i桁目の数字
template<typename T>void press(T &v){v.erase(unique(ALL(v)),v.end());} // 圧縮
Vi zip(Vi b){int Z=b.size(); // 座標圧縮
Pii p[Z+10];int a=b.size();Vi l(a);for(int i=0;i<a;i++)
p[i]=mp(b[i],i);sort(p,p+a);int w=0;for(int i=0;i<a;i++)
{if(i&&p[i].first!=p[i-1].first)w++;l[p[i].second]=w;}return l;}
int SMALLER(Vi &a,int x){return lower_bound(a.begin(),a.end(),x)-a.begin();}
int orSMALLER(Vi &a,int x){return upper_bound(a.begin(),a.end(),x)-a.begin();}
int BIGGER(Vi &a,int x){return a.size()-orSMALLER(a,x);}
int orBIGGER(Vi &a,int x){return a.size()-SMALLER(a,x);}
int COUNT(Vi &a,int x) {return upper_bound(ALL(a),x)-lower_bound(ALL(a),x);}
int maxind(Vi &a){return max_element(ALL(a))-a.begin();}
int minind(Vi &a){return min_element(ALL(a))-a.begin();}

//const int MOD = 998244353;
const int MOD = 1000000007;
const double EPS = 1e-6;
using mint = modint;

void init(){cin.tie(0);cout.tie(0);ios::sync_with_stdio(0);
cout<<fixed<<setprecision(12);mint::set_mod(MOD);}

/************************************ START ************************************/

Vi dx = {0,1,0,-1};
Vi dy = {1,0,-1,0};

signed main() {
  init();
  int h,w;cin >> h >> w;
  Vs mapp(h);Vin(mapp);
  map<int,Pii> ma;
  VVi tm(h,Vi(w));
  int ct = 1;
  rep(i,0,h){
    if(i%2==0) rep(j,0,w){
      tm[i][j] = ct;
      ma[ct] = mp(i,j);
      ct++;
    }
    else repreq(j,w-1,0){
      tm[i][j] = ct;
      ma[ct] = mp(i,j);
      ct++;
    }
  }
  //cout << tm << endl;
  mf_graph<int> gr(h*w+2);
  int S,G;
  S = 0;
  G = h*w+1;
  repeq(i,1,h*w){
    if(mapp[ma[i].FI][ma[i].SE]=='#') continue;
    if(i%2) gr.add_edge(S,i,1);
    else gr.add_edge(i,G,1);
  }
  
  auto inside = [&] (int i,int j){
    if(i < 0 || j < 0 || i >= h || j >= w) return 0;
    else return 1;
  };
  
  rep(i,0,h)rep(j,0,w){
    if(mapp[i][j]=='#') continue;
    if(tm[i][j]%2==0) continue;
    rep(k,0,4){
      if(inside(i+dx[k],j+dy[k]) && mapp[i+dx[k]][j+dy[k]]=='.'){
        gr.add_edge(tm[i][j],tm[i+dx[k]][j+dy[k]],1);
      }
    }
  }
  cout << gr.flow(S,G) << endl;
  auto ed = gr.edges();
  rep(i,0,ed.size()) {
    if(ed[i].flow){
      Pii s,t;
      
      if(!(ed[i].from >= 1&&ed[i].to>=1&&ed[i].from<=h*w&&ed[i].to<=h*w)) continue;
      s = ma[ed[i].from];
      t = ma[ed[i].to];
      if(t.SE-s.SE == 1) {mapp[s.FI][s.SE] = '>';mapp[t.FI][t.SE] = '<';}
      if(t.SE-s.SE == -1) {mapp[s.FI][s.SE] = '<';mapp[t.FI][t.SE] = '>';}
      if(t.FI-s.FI == 1) {mapp[s.FI][s.SE] = 'v';mapp[t.FI][t.SE] = '^';}
      if(t.FI-s.FI == -1) {mapp[s.FI][s.SE] = '^';mapp[t.FI][t.SE] = 'v';}
    }
  }
  rep(i,0,h) cout << mapp[i] << endl;
  return 0;
}

Measured memory_bytes: 7008