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

#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;
}


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;

    atcoder::mf_graph<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.flow(s, t) << "\n";

    auto edges = mf.edges();
    for(auto &e : edges){
      if(e.flow != 0 and e.from != s and e.to != t){
        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: 5932