#include <bits/stdc++.h>

#ifdef DEBUG
#include <Mylib/Debug/debug.cpp>
#else
#define dump(...) ((void)0)
#endif

template <typename T, typename U>
bool chmin(T &a, const U &b){
  return (a > b ? a = b, true : false);
}

template <typename T, typename U>
bool chmax(T &a, const U &b){
  return (a < b ? a = b, true : false);
}

template <typename T, size_t N, typename U>
void fill_array(T (&a)[N], const U &v){
  std::fill((U*)a, (U*)(a + N), v);
}

template <typename T, size_t N, size_t I = N>
auto make_vector(const std::array<int, N> &a, T value = T()){
  static_assert(I >= 1);
  static_assert(N >= 1);
  if constexpr (I == 1){
    return std::vector<T>(a[N - I], value);
  }else{
    return std::vector(a[N - I], make_vector<T, N, I - 1>(a, value));
  }
}

template <typename T>
std::ostream& operator<<(std::ostream &s, const std::vector<T> &a){
  for(auto it = a.begin(); it != a.end(); ++it){
    if(it != a.begin()) s << " ";
    s << *it;
  }
  return s;
}

template <typename T>
std::istream& operator>>(std::istream &s, std::vector<T> &a){
  for(auto &x : a) s >> x;
  return s;
}

/**
 * @title Push-relabel
 * @docs push_relabel.md
 */
namespace haar_lib {
  template <typename T>
  struct push_relabel {
  private:
    struct edge {
      int from, to, rev;
      T cap;
      bool is_rev;
    };

    int N;
    std::vector<std::vector<edge>> g;
    std::vector<T> excess;
    std::vector<int> height;
    std::queue<int> next_active_vertex;
    constexpr static T inf = std::numeric_limits<T>::max();

    void init(int s, int t){
      excess[s] = inf;

      for(auto &e : g[s]){
        push(e, s, t);
      }

      {
        for(int i = 0; i < N; ++i){
          height[i] = N;
        }

        std::queue<int> q;
        std::vector<bool> check(N);
        q.push(t);
        height[t] = 0;

        while(not q.empty()){
          const int i = q.front(); q.pop();

          if(check[i]) continue;
          check[i] = true;

          for(auto &e : g[i]){
            if(not e.is_rev) continue;
            if(height[e.from] + 1 < height[e.to]){
              height[e.to] = height[e.from] + 1;
              q.push(e.to);
            }
          }
        }

        height[s] = N;
      }
    }

    bool is_pushable(const edge &e){
      if(excess[e.from] == 0) return false;
      if(height[e.from] != height[e.to] + 1) return false;
      if(e.cap == 0) return false;
      return true;
    }

    void push(edge &e, int, int){
      auto &r = g[e.to][e.rev];

      T flow = std::min(e.cap, excess[e.from]);

      e.cap -= flow;
      r.cap += flow;

      excess[e.from] -= flow;
      excess[e.to] += flow;

      if(excess[e.to] == flow) next_active_vertex.push(e.to);
    }

    void relabel(int i, int, int){
      int a = std::numeric_limits<int>::max() / 2;
      for(auto &e : g[i]){
        if(e.cap > 0) a = std::min(a, height[e.to]);
      }

      height[i] = a + 1;
    }

  public:
    push_relabel(){}
    push_relabel(int N): N(N), g(N), excess(N), height(N){}

    void add_edge(int from, int to, T c){
      g[from].push_back({from, to, (int)g[to].size(), c, false});
      g[to].push_back({to, from, (int)g[from].size() - 1, 0, true});
    }

    T solve(int s, int t){
      init(s, t);

      while(true){
        int index = -1;

        while(not next_active_vertex.empty()){
          int i = next_active_vertex.front();
          if(i != s and i != t and excess[i] > 0){
            index = i;
            break;
          }
          next_active_vertex.pop();
        }

        if(index == -1) break;

        bool ok = false;
        for(auto &e : g[index]){
          if(is_pushable(e)){
            push(e, s, t);
            ok = true;
            break;
          }
        }

        if(not ok){
          relabel(index, s, t);
        }
      }

      return excess[t];
    }

    std::vector<edge> edges() const {
      std::vector<edge> ret;
      for(auto &v : g) ret.insert(ret.end(), v.begin(), v.end());
      return ret;
    }
  };
}



namespace haar_lib {}

namespace solver {
  using namespace haar_lib;

  void init(){
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed << std::setprecision(12);
    std::cerr << std::fixed << std::setprecision(12);
    std::cin.exceptions(std::ios_base::failbit);
  }

  int dir[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};

  void solve(){
    int N, M; std::cin >> N >> M;
    std::vector<std::string> S(N); std::cin >> S;

    push_relabel<int> mf(N * M * 2 + 2);

    int s, t;
    auto index = make_vector<int, 2>({N, M});
    auto rev = std::vector<std::pair<int, int>>(N * M);

    {
      int k = 0;

      for(int i = 0; i < N; ++i){
        for(int j = 0; j < M; ++j){
          index[i][j] = k++;
          rev[index[i][j]] = std::make_pair(i, j);
        }
      }

      s = k++;
      t = k++;
    }

    for(int i = 0; i < N; ++i){
      for(int j = 0; j < M; ++j){
        if(S[i][j] == '#') continue;
        if((i + j) % 2 == 0){
          mf.add_edge(s, index[i][j], 1);
        }else{
          mf.add_edge(index[i][j], t, 1);
        }
      }
    }

    for(int i = 0; i < N; ++i){
      for(int j = 0; j < M; ++j){
        if((i + j) % 2 == 1 or S[i][j] == '#') continue;
        for(auto [dx, dy] : dir){
          int x = i + dx, y = j + dy;
          if(x < 0 or x >= N or y < 0 or y >= M or S[x][y] == '#') continue;
          mf.add_edge(index[i][j], index[x][y], 1);
        }
      }
    }

    std::cout << mf.solve(s, t) << "\n";

    auto edges = mf.edges();
    for(auto &e : edges){
      if(e.cap == 0 and e.from != s and e.to != t and not e.is_rev){
        auto [x1, y1] = rev[e.from];
        auto [x2, y2] = rev[e.to];

        if(x1 == x2){
          if(y1 == y2 + 1){
            S[x1][y1] = '<';
            S[x1][y2] = '>';
          }else{
            S[x1][y1] = '>';
            S[x1][y2] = '<';
          }
        }else{
          if(x1 == x2 + 1){
            S[x1][y1] = '^';
            S[x2][y2] = 'v';
          }else{
            S[x1][y1] = 'v';
            S[x2][y2] = '^';
          }
        }
      }
    }

    for(int i = 0; i < N; ++i) std::cout << S[i] << "\n";
  }
}

int main(){
  solver::init();
  while(true){
    try{
      solver::solve();
    }catch(const std::istream::failure &e){
      break;
    }
  }
  return 0;
}


Measured memory_bytes: 7260