/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author aajisaka
 */

#include<bits/stdc++.h>

using namespace std;

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

#define SPEED ios_base::sync_with_stdio(false);cin.tie(nullptr)
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

using ll = long long;
using ull = unsigned long long;
using P = pair<ll, ll>;

constexpr long double PI = 3.14159265358979323846264338327950288L;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// Original: https://img.atcoder.jp/practice2/ac-library.zip

#include <cassert>
#include <limits>
#include <queue>
#include <vector>

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

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

      auto bfs = [&]() {
          std::fill(level.begin(), level.end(), -1);
          level[s] = 0;
          while(!que.empty()) que.pop(); // que.clear();
          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, std::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;
        std::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;
    }

    std::vector<bool> min_cut(int s) {
      std::vector<bool> visited(_n);
      std::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;
    };
    std::vector<std::pair<int, int>> pos;
    std::vector<std::vector<_edge>> g;
};


class DMaxflow {
public:
    void solve(istream& cin, ostream& cout) {
      SPEED;
      int n, m; cin >> n >> m;
      vector<string> mat(n);
      rep(i, n) {
        cin >> mat[i];
      }
      auto mf = mf_graph<int>(n*m+2);
      for(int i=0; i<n; i++) {
        for(int j=0; j<m; j++) {
          if (mat[i][j] == '.') {
            if ((i+j)%2==0) {
              mf.add_edge(n*m, i*m+j, 1);
            } else {
              mf.add_edge(i*m+j, n*m+1, 1);
            }
          }
        }
      }

      vector<int> pos;
      vector<P> ds;
      vector<P> directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};

      for(int i=0; i<n; i++) {
        for(int j=0; j<m; j++) {
          if (mat[i][j] == '.' && (i+j)%2 == 0) {
            for(auto e: directions) {
              int u = i+e.first;
              int v = j+e.second;
              if (0 <= u && u < n && 0 <= v && v < m && mat[u][v] == '.') {
                int idx = mf.add_edge(i*m+j, u*m+v, 1);
                pos.push_back(idx);
                ds.push_back(e);
              }
            }
          }
        }
      }

      int ret = mf.flow(n*m, n*m+1);

      for(int i=0; i<pos.size(); i++) {
        auto p = mf.get_edge(pos[i]);
        if (p.flow == 1) {
          int x = p.from/m;
          int y = p.from%m;
          debug(x, y, ds[i].first, ds[i].second);
          if (ds[i] == P(1, 0)) {
            mat[x][y] = 'v';
            mat[x+1][y] = '^';
          } else if (ds[i] == P(-1, 0)) {
            mat[x][y] = '^';
            mat[x-1][y] = 'v';
          } else if (ds[i] == P(0, -1)) {
            mat[x][y] = '<';
            mat[x][y-1] = '>';
          } else if (ds[i] == P(0, 1)) {
            mat[x][y] = '>';
            mat[x][y+1] = '<';
          }
        }
      }

      cout << ret << '\n';
      for(auto& e: mat) {
        cout << e << '\n';
      }

    }
};

signed main() {
  DMaxflow solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}

Measured memory_bytes: 5624