#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n) for(int i=0; i<n; i++)
#define REPR(i, n) for(int i=n-1; i>=0; i--)
#define FOR(i, m, n) for(int i=m; i<n; i++)
#define ALL(v) v.begin(), v.end()
#define SIZE(x) ll(x.size()) 
using P = pair<int, int>;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = 1e9;
const ll LINF = (1LL<<60);

template <class Cap> struct mf_graph {
  public:
    mf_graph() : _n(0) {}
    mf_graph(int n) : _n(n), g(n) {}

    int add_edge(int from, int to, Cap cap) {
      assert(0 <= from && from < _n);
      assert(0 <= to && to < _n);
      assert(0 <= cap);
      int m = int(pos.size());
      pos.push_back({from, int(g[from].size())});
      g[from].push_back(_edge{to, int(g[to].size()), cap});
      g[to].push_back(_edge{from, int(g[from].size()) - 1, 0});
      return m;
    }

    struct edge {
      int from, to;
      Cap cap, flow;
    };

    edge get_edge(int i) {
      int m = int(pos.size());
      assert(0 <= i && i < m);
      auto _e = g[pos[i].first][pos[i].second];
      auto _re = g[_e.to][_e.rev];
      return edge{pos[i].first, _e.to, _e.cap + _re.cap, _re.cap};
    }
    vector<edge> edges() {
      int m = int(pos.size());
      std::vector<edge> result;
      for (int i = 0; i < m; i++) {
        result.push_back(get_edge(i));
      }
      return result;
    }
    void change_edge(int i, Cap new_cap, Cap new_flow) {
      int m = int(pos.size());
      assert(0 <= i && i < m);
      assert(0 <= new_flow && new_flow <= new_cap);
      auto& _e = g[pos[i].first][pos[i].second];
      auto& _re = g[_e.to][_e.rev];
      _e.cap = new_cap - new_flow;
      _re.cap = new_flow;
    }

    Cap flow(int s, int t) {
      return flow(s, t, numeric_limits<Cap>::max());
    }
    Cap flow(int s, int t, Cap flow_limit) {
      assert(0 <= s && s < _n);
      assert(0 <= t && t < _n);

      vector<int> level(_n), iter(_n);
      queue<int> que;

      auto bfs = [&]() {
        fill(level.begin(), level.end(), -1);
        level[s] = 0;
        queue<int>().swap(que);
        que.push(s);
        while (!que.empty()) {
          int v = que.front();
          que.pop();
          for (auto e : g[v]) {
            if (e.cap == 0 || level[e.to] >= 0) continue;
            level[e.to] = level[v] + 1;
            if (e.to == t) return;
            que.push(e.to);
          }
        }
      };
      auto dfs = [&](auto self, int v, Cap up) {
        if (v == s) return up;
        Cap res = 0;
        int level_v = level[v];
        for (int& i = iter[v]; i < int(g[v].size()); i++) {
          _edge& e = g[v][i];
          if (level_v <= level[e.to] || g[e.to][e.rev].cap == 0) continue;
          Cap d = self(self, e.to, min(up - res, g[e.to][e.rev].cap));
          if (d <= 0) continue;
          g[v][i].cap += d;
          g[e.to][e.rev].cap -= d;
          res += d;
          if (res == up) break;
        }
        return res;
      };

      Cap flow = 0;
      while (flow < flow_limit) {
        bfs();
          if (level[t] == -1) break;
        fill(iter.begin(), iter.end(), 0);
        while (flow < flow_limit) {
          Cap f = dfs(dfs, t, flow_limit - flow);
          if (!f) break;
          flow += f;
        }
      }
      return flow;
    }

    vector<bool> min_cut(int s) {
      vector<bool> visited(_n);
      queue<int> que;
      que.push(s);
      while (!que.empty()) {
        int p = que.front();
        que.pop();
        visited[p] = true;
        for (auto e : g[p]) {
          if (e.cap && !visited[e.to]) {
            visited[e.to] = true;
            que.push(e.to);
          }
        }
      }
      return visited;
    }

  private:
    int _n;
    struct _edge {
      int to, rev;
      Cap cap;
    };
    vector<pair<int, int>> pos;
    vector<vector<_edge>> g;
};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n,m; cin >> n >> m;
  vector<string> field(n);
  REP(i,n) cin >> field[i];

  mf_graph<int> g(n*m+2);
  int s = n*m;
  int t = n*m+1;

  REP(i,n) REP(j,m){
    if(field[i][j]=='#') continue;
    int ind = i*m+j;
    if((i+j)%2==0) g.add_edge(s,ind,1); // s -> even
    else g.add_edge(ind,t,1); // odd -> t
  }

  // even -> odd
  REP(i,n) REP(j,m){
    if((i+j)%2 || field[i][j]=='#') continue;
    int ind = i*m+j;
    if(i && field[i-1][j]=='.'){
      int ind2 = (i-1)*m+j;
      g.add_edge(ind,ind2,1);
    }
    if(j && field[i][j-1]=='.'){
      int ind2 = i*m+j-1;
      g.add_edge(ind,ind2,1);
    }
    if(i+1<n && field[i+1][j]=='.'){
      int ind2 = (i+1)*m+j;
      g.add_edge(ind,ind2,1);
    }
    if(j+1<m && field[i][j+1]=='.'){
      int ind2 = i*m+j+1;
      g.add_edge(ind,ind2,1);
    }
  }

  cout << g.flow(s,t) << '\n';

  auto edges = g.edges();
  for(auto e: edges){
    if(e.from==s || e.to==t || 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){
      field[i1][j1] = 'v';
      field[i0][j0] = '^';
    }else if(j0==j1+1){
      field[i1][j1] = '>';
      field[i0][j0] = '<';
    }else if(i0==i1-1){
      field[i1][j1] = '^';
      field[i0][j0] = 'v';
    }else if(j0==j1-1){
      field[i1][j1] = '<';
      field[i0][j0] = '>';
    }
  }
  
  REP(i,n) cout << field[i] << '\n';

  return 0;
}



Measured memory_bytes: 5760