#include "atcoder/all"
#include <algorithm>
#include <bitset>
#include <cmath>
#include <complex>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <vector>

const int MOD = 1e9 + 7;
const int iINF = 2147483647 / 2;
const long long int llINF = 9223372036854775807 / 2;

using namespace std;
using namespace atcoder;
using ll = long long int;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using vvvl = vector<vector<vector<ll>>>;

typedef pair<ll, ll> pll;
bool paircomp(const pll &a, const pll &b) {
  if (a.first == b.first)
    return a.second < b.second;
  return a.first < b.first;
}

#define REP(i, n) for (ll i = 0; i < (n); i++)
#define RREP(i, n) for (ll i = (n)-1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define AUTO(i, m) for (auto &i : m)
#define ALL(a) (a).begin(), (a).end()
#define MAX(vec) *std::max_element(vec.begin(), vec.end())
#define MIN(vec) *std::min_element(vec.begin(), vec.end())
#define ARGMAX(vec)                                                            \
  std::distance(vec.begin(), std::max_element(vec.begin(), vec.end()))
#define ARGMIN(vec)                                                            \
  std::distance(vec.begin(), std::min_element(vec.begin(), vec.end()))
#define REV(T) greater<T>()
#define PQ(T) priority_queue<T, vector<T>, greater<T>>
#define VVL(a, b, c) vector<vector<ll>>(a, vector<ll>(b, c))
#define VV(T, a, b, c) vector<vector<T>>(a, vector<T>(b, c))
#define VVVL(a, b, c, d)                                                       \
  vector<vector<vector<ll>>>(a, vector<vector<ll>>(b, vector<ll>(c, d)))
#define VVV(T, a, b, c, d)                                                     \
  vector<vector<vector<T>>>(a, vector<vector<T>>(b, vector<T>(c, d)))
#define SP(a) fixed << setprecision(a)
#define SQRT(a) sqrt((long double)(a))
#define DPOW(a, b) pow((long double)(a), (long double)(b))
#define UNIQUE(vec)                                                            \
  do {                                                                         \
    sort(ALL((vec)));                                                          \
    (vec).erase(std::unique(ALL((vec))), (vec).end());                         \
  } while (0)

ll POW(ll n, ll m) {
  if (m == 0) {
    return 1;
  } else if (m % 2 == 0) {
    ll tmp = POW(n, m / 2);
    return (tmp * tmp);
  } else {
    return (n * POW(n, m - 1));
  }
}

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ll N, M;
  cin >> N >> M;
  vector<string> S(N);
  REP(i, N) cin >> S[i];

  mf_graph<ll> graph(N * M + 2);

  REP(i, N) REP(j, M) {
    if (S[i][j] == '#')
      continue;
    if ((i + j) % 2 == 0)
      graph.add_edge(N * M, i * M + j, 1);
    else
      graph.add_edge(i * M + j, N * M + 1, 1);
  }

  REP(i, N) {
    REP(j, M) {
      if ((i + j) % 2 == 1 || S[i][j] == '#')
        continue;
      if (i - 1 >= 0 && S[i - 1][j] == '.')
        graph.add_edge(i * M + j, i * M - M + j, 1);
      if (j - 1 >= 0 && S[i][j - 1] == '.')
        graph.add_edge(i * M + j, i * M + j - 1, 1);
      if (i + 1 < N && S[i + 1][j] == '.')
        graph.add_edge(i * M + j, i * M + M + j, 1);
      if (j + 1 < M && S[i][j + 1] == '.')
        graph.add_edge(i * M + j, i * M + j + 1, 1);
    }
  }
  cout << graph.flow(N * M, N * M + 1) << endl;

  AUTO(e, graph.edges()) {
    if (e.from == N * M || e.to == N * M + 1 || e.flow == 0)
      continue;
    ll i0 = e.from / M, j0 = e.from % M;
    ll i1 = e.to / M, j1 = e.to % M;

    if (i0 == i1 + 1) {
      S[i1][j1] = 'v';
      S[i0][j0] = '^';
    } else if (j0 == j1 + 1) {
      S[i1][j1] = '>';
      S[i0][j0] = '<';
    } else if (i0 == i1 - 1) {
      S[i0][j0] = 'v';
      S[i1][j1] = '^';
    } else {
      S[i0][j0] = '>';
      S[i1][j1] = '<';
    }
  }
  REP(i, N) cout << S[i] << endl;

  return 0;
}


Measured memory_bytes: 6164