/*	author:  Kite_kuma
	created: 2020.09.07 13:15:54 */

#include <bits/stdc++.h>
using namespace std;

#pragma region aliases

#define rep(i, n) for(long long i = 0; i < (n); i++)
#define rrep(i, n) for(long long i = (n)-1; i > -1; i--)
#define Rep(i, m, n) for(long long i = (m); i < (n); i++)
#define rRep(i, m, n) for(long long i = (n)-1; i >= (m); i--)
#define REP(i, m, n, p) for(long long i = m; i < n; i += p)
#define foa(s, v) for(auto &s : v)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define bcnt(n) __builtin_popcountll(n)
#define endk endl
#define ednl endl
#define enld endl

using ll = long long;
using ld = long double;
using ull = unsigned long long;
using vb = vector<bool>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vvvi = vector<vector<vector<int>>>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using mll = map<long long, long long>;
using pll = pair<long long, long long>;
using qll = queue<long long>;
using sll = set<long long>;
using vpll = vector<pair<long long, long long>>;
template <class T = ll>
using V = vector<T>;
template <class T = ll>
using VV = V<V<T>>;
template <class T = ll>
using VVV = V<V<V<T>>>;
//昇順pq(小さい方から取り出す)
template <class T = ll>
using pqup = priority_queue<T, vector<T>, greater<T>>;
//降順pq(大きい方から取り出す)
template <class T = ll>
using pqdn = priority_queue<T>;

#pragma endregion

#pragma region constants

long long const limLL = 9223372036854775807;  // POW(2,63)-1 ~ 9.22e18
long long const dekai = 3e16;
const long double pi = acos(-1);
const char el = '\n';
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int ddx[8] = {-1, -1, -1, 0, 0, 1, 1, 1};
int ddy[8] = {-1, 0, 1, -1, 1, -1, 0, 1};

const int mod = 1000000007;
// const int mod = 998244353;

#pragma endregion

#pragma region basic_procedure

template <class T>
inline bool isin(T x, T lef, T rig) {
	return ((lef <= x) && (x < rig));
}

template <class T>
inline bool chmin(T &a, T b) {
	if(a > b) {
		a = b;
		return true;
	}
	return false;
}
template <class T>
inline bool chmax(T &a, T b) {
	if(a < b) {
		a = b;
		return true;
	}
	return false;
}

void Yes(bool f = 1) { cout << (f ? "Yes" : "No") << "\n"; }
void No() { cout << "No\n"; }
void YES(bool f = 1) { cout << (f ? "YES" : "NO") << "\n"; }
void NO() { cout << "NO\n"; }
template <class T>
void drop(T answer) {
	cout << answer << "\n";
	exit(0);
}
void err() {
	cout << -1 << "\n";
	exit(0);
}

vector<long long> vin(long long n) {  //整数n個の入力を受け取ってベクトルに突っ込んで返す
	vector<long long> v(n);
	for(long long i = 0; i < n; i++) {
		cin >> v[i];
	}
	return v;
}

//ベクトルの出力(検証済)
// vectorの中身を出力する 答えの出力に利用可能
template <class T>
void vout(vector<T> &v, bool tate = 0) {
	if(v.size() > 0) {
		for(auto it = v.begin(); it < v.end(); it++) {
			cout << *it;
			if(it != v.end() - 1) {
				if(tate)
					cout << endl;
				else
					cout << " ";
			}
		}
	}
	cout << endl;
}

template <class T>
void add(vector<T> &v, T val) {	 //ベクトルの各要素に加算
	for(auto &a : v) a += val;
	return;
}

// vectorの中身を数える map<要素,個数>を返す
template <class T>
map<T, long long> cntv(vector<T> v) {
	map<T, long long> m;
	for(auto &g : v) {
		if(m.count(g))
			m[g]++;
		else
			m[g] = 1;
	}
	return m;
}

//配列圧縮(検証済)
//{1,36,1,3,8,-2,-92}を
//{2, 5,2,3,4, 1,  0}にする
template <class T>
vector<long long> press(vector<T> &v) {
	long long n = v.size();
	vector<long long> w(n);
	map<T, long long> m;
	for(T &p : v) m[p] = 0;
	long long i = 0;
	for(auto &p : m) {
		p.second = i;
		i++;
	}
	for(long long i = 0; i < n; i++) w.at(i) = m[v.at(i)];
	return w;
}

template <class T>
T divup(T a, T b) {
	//端数繰りあがり割り算
	assert(b != 0);
	T x = abs(a);
	T y = abs(b);
	T z = (x + y - 1) / y;
	if((a < 0 && b > 0) || (a > 0 && b < 0))
		return -z;
	else if(a == 0)
		return 0;
	else
		return z;
}

long long POW(long long a, long long n) {
	long long res = 1;
	while(n > 0) {
		if(n & 1) res = res * a;
		a = a * a;
		n >>= 1;
	}
	return res;
}

template <class T>
int sgn(T x) {	//符号関数
	if(x < 0) return -1;
	if(x == 0) return 0;
	return 1;
}

long long modpow(long long a, long long n, long long mod) {	 // a^n mod
	if(mod == 1) return 0LL;
	long long res = 1;
	while(n > 0) {
		if(n & 1) res = res * a % mod;
		a = a * a % mod;
		n >>= 1;
	}
	return res;
}

// a * x % mod == __gcd(a,mod)なるxを返す
// a が modの倍数でないことが条件
long long modinv(long long a, long long mod) {
	long long b = mod, u = 1, v = 0;
	while(b) {
		long long t = a / b;
		a -= t * b;
		swap(a, b);
		u -= t * v;
		swap(u, v);
	}
	u %= mod;
	if(u < 0) u += mod;
	return u;
}

vvll comb(100, vll(100, -1));
long long com(long long n, long long k) {  //普通の二項計数(overflowに注意)
	assert(n < 100 && k < 100);
	if(n < k || k < 0 || n < 0) return 0;
	if(comb[n][k] != -1) return comb[n][k];
	ll res;
	if(n - k < k)
		res = com(n, n - k);
	else if(k == 0)
		res = 1;
	else
		res = com(n - 1, k - 1) + com(n - 1, k);
	comb[n][k] = res;
	return res;
}

// nCk modを求める
const ll MAX = 5100000;
// この値は求める二項計数の値に応じて変える
// MAX=3*10^7のとき1900msほど、ほぼ比例
// MAX=5*10^6程度ならそれほど気にしなくてよい(300ms程)
long long fac[MAX], finv[MAX], inv[MAX];

void cominit() {
	// テーブルを作る前処理
	fac[0] = fac[1] = 1;
	finv[0] = finv[1] = 1;
	inv[1] = 1;
	for(ll i = 2; i < MAX; i++) {
		fac[i] = fac[i - 1] * i % mod;
		inv[i] = mod - inv[mod % i] * (mod / i) % mod;
		finv[i] = finv[i - 1] * inv[i] % mod;
	}
}
long long commod(ll n, ll k) {	// 二項係数計算
	if(n < k) return 0;
	if(n < 0 || k < 0) return 0;
	return fac[n] * (finv[k] * finv[n - k] % mod) % mod;
}
long long pmod(ll n, ll k) {  //順列計算
	if(n < k) return 0;
	if(n < 0 || k < 0) return 0;
	return fac[n] * finv[n - k] % mod;
}
long long hmod(ll n, ll k) {  // nHk計算
	// n個の区別しないoを区別するk個の箱に入れる方法の総数
	//(n+k-1)C(k-1)と等しい
	return commod(n + k - 1, n);
}
#pragma endregion

#pragma region input
#define VEC(type, name, size) \
	vector<type> name(size);  \
	INPUT(name)
#define VVEC(type, name, h, w)                     \
	vector<vector<type>> name(h, vector<type>(w)); \
	INPUT(name)
#define INT(...)     \
	int __VA_ARGS__; \
	INPUT(__VA_ARGS__)
#define LL(...)            \
	long long __VA_ARGS__; \
	INPUT(__VA_ARGS__)
#define STR(...)        \
	string __VA_ARGS__; \
	INPUT(__VA_ARGS__)
#define CHAR(...)     \
	char __VA_ARGS__; \
	INPUT(__VA_ARGS__)
#define DOUBLE(...)     \
	double __VA_ARGS__; \
	INPUT(__VA_ARGS__)
#define LD(...)              \
	long double __VA_ARGS__; \
	INPUT(__VA_ARGS__)

template <class T>
void scan(T &a) {
	cin >> a;
}
template <class T>
void scan(vector<T> &a) {
	for(auto &i : a) scan(i);
}
template <class T, class L>
void scan(pair<T, L> &p) {
	scan(p.first);
	scan(p.second);
}
void INPUT() {}
template <class Head, class... Tail>
void INPUT(Head &head, Tail &... tail) {
	scan(head);
	INPUT(tail...);
}
template <class T>
inline void print(T x) {
	cout << x << '\n';
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
	is >> p.first >> p.second;
	return is;
}
#pragma endregion

#pragma region debug

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
	os << p.first << " " << p.second;
	return os;
}

template <class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
	rep(i, v.size()) {
		if(i) os << " ";
		os << v[i];
	}
	return os;
}

template <typename T>
void view(const std::vector<T> &v) {
	std::cerr << "{ ";
	for(const auto &e : v) {
		std::cerr << e << ", ";
	}
	std::cerr << "\b\b }";
}
template <typename T>
void view(const std::vector<std::vector<T>> &vv) {
	std::cerr << "{\n";
	for(const auto &v : vv) {
		std::cerr << "\t";
		view(v);
		cerr << "\n";
	}
	std::cerr << "}";
}
template <typename T, typename U>
void view(const std::vector<std::pair<T, U>> &v) {
	std::cerr << "{\n";
	for(const auto &c : v) {
		std::cerr << "\t(" << c.first << ", " << c.second << ")\n";
	}
	std::cerr << "}";
}
template <typename T, typename U>
void view(const std::map<T, U> &m) {
	std::cerr << "{\n";
	for(auto &t : m) {
		std::cerr << "\t[" << t.first << "] : " << t.second << "\n";
	}
	std::cerr << "}";
}
template <typename T, typename U>
void view(const std::pair<T, U> &p) {
	std::cerr << "(" << p.first << ", " << p.second << ")";
}
template <typename T>
void view(const std::set<T> &s) {
	std::cerr << "{ ";
	for(auto &t : s) {
		view(t);
		std::cerr << ", ";
	}
	std::cerr << "\b\b }";
}
template <typename T>
void view(T e) {
	std::cerr << e;
}

// when debugging : g++ foo.cpp -DLOCAL
#ifdef LOCAL
void debug_out() {}
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
	view(H);
	cerr << ", ";
	debug_out(T...);
}
#define debug(...)                                           \
	do {                                                     \
		cerr << __LINE__ << " [" << #__VA_ARGS__ << "] : ["; \
		debug_out(__VA_ARGS__);                              \
		cerr << "\b\b]\n";                                   \
	} while(0)
#define dump(x)                                 \
	do {                                        \
		cerr << __LINE__ << " " << #x << " : "; \
		view(x);                                \
		cerr << "\n";                           \
	} while(0)
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif

#pragma endregion

template <class T = long long>
struct edge_cap {
	T cap;
	int from;
	int to;
	int rev;  // fromの方の配列で逆辺が何番目に存在するか
};
template <class T = long long>
class Dinic {
   private:
   public:
	int ver;  //頂点数
	vector<vector<edge_cap<T>>> edges;
	vector<int> level;
	vector<int> chk;

	Dinic() = default;
	Dinic(int vertex) : ver(vertex), edges(vertex), level(vertex, -1), chk(vertex, 0) {}

	//辺と逆辺の追加 (0-indexed)
	void update(int from, int to, T cap = 1) {
		edge_cap<T> e;
		e.cap = cap;
		e.from = from;
		e.to = to;
		e.rev = (int)edges[to].size();
		edges[from].push_back(e);

		e.cap = (T)0;
		swap(e.to, e.from);
		e.rev = (int)edges[from].size() - 1;
		edges[to].push_back(e);
	}

	//入力受取 (1-indexed)
	void input(int edge_num, int index = 1) {
		for(int i = 0; i < edge_num; i++) {
			int a;
			int b;
			T cap;
			cin >> a >> b >> cap;
			a -= index;
			b -= index;
			update(a, b, cap);
		}
	}

	//有効な辺のみを用いた幅優先探索で距離を求める
	void bfs(int s) {
		level.assign(ver, -1);
		level[s] = 0;
		queue<int> q;
		q.push(s);
		while(!q.empty()) {
			int now = q.front();
			q.pop();
			for(auto &e : edges[now]) {
				if(level[e.to] >= 0) continue;
				if(e.cap <= 0) continue;
				level[e.to] = level[now] + 1;
				q.push(e.to);
			}
		}
		return;
	}

	//流せる辺を探す
	T dfs(int now, int t, T f) {
		if(now == t) return f;
		for(int i = chk[now]; i < (int)edges[now].size(); i++) {
			auto &e = edges[now][i];
			if(level[now] + 1 != level[e.to] || e.cap <= 0) {
				chk[now]++;
				continue;
			}
			T k = dfs(e.to, t, min(f, e.cap));
			if(k > 0) {
				e.cap -= k;
				edges[e.to][e.rev].cap += k;
				return k;
			}
			chk[now]++;
		}
		return (T)0;
	}

   public:
	T maxflow(int s, int t) {
		T flow = 0;
		const T INF = 3e16;	 // T == int だとバグる
		while(1) {
			bfs(s);
			if(level[t] < 0) return flow;
			for(int i = 0; i < ver; i++) chk[i] = 0;
			T fl = 1;
			while(fl > 0) {
				fl = dfs(s, t, INF);
				flow += fl;
			}
		}
	}
};

#include <atcoder/maxflow>

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << fixed << setprecision(15);
	srand((unsigned)time(NULL));

	INT(n, m);
	VEC(string, s, n);

	int h = n * m;

	vvi a(n, vi(m));

	// Dinic<> din(n * m + 2);
	atcoder::mf_graph<ll> din(n * m + 2);

	int source = n * m, terminal = n * m + 1;

	auto con = [&](int a, int b) { return a * m + b; };

	rep(i, n) rep(j, m) {
		if(s[i][j] == '#') continue;
		if((i - j) % 2 == 0) {
			if(i && s[i][j] == '.' && s[i - 1][j] == '.') {
				din.add_edge(con(i, j), con(i - 1, j), 1);
			}
			if(j && s[i][j] == '.' && s[i][j - 1] == '.') {
				din.add_edge(con(i, j), con(i, j - 1), 1);
			}
			if(i + 1 < n && s[i][j] == '.' && s[i + 1][j] == '.') {
				din.add_edge(con(i, j), con(i + 1, j), 1);
			}
			if(j + 1 < m && s[i][j] == '.' && s[i][j + 1] == '.') {
				din.add_edge(con(i, j), con(i, j + 1), 1);
			}
			din.add_edge(source, con(i, j), 1);
		} else {
			din.add_edge(con(i, j), terminal, 1);
		}
	}

	cout << (din.flow(source, terminal)) << el;

	foa(e, din.edges()) {
		debug(e.from, e.to, e.cap);
		int k = e.from / m, l = e.from % m;
		if((k - l) % 2 != 0 || e.from >= source) continue;
		if(e.to < source && e.flow) {
			int a, b;
			a = e.to / m, b = e.to % m;
			if(k == a) {
				if(l < b) {
					s[k][l] = '>';
					s[a][b] = '<';
				} else {
					s[k][l] = '<';
					s[a][b] = '>';
				}
			} else if(k < a) {
				s[k][l] = 'v';
				s[a][b] = '^';
			} else {
				s[k][l] = '^';
				s[a][b] = 'v';
			}
			debug(k, l, a, b);
		}
	}
	dump(s);

	rep(i, n) { cout << s[i] << el; }

	return 0;
}


Measured memory_bytes: 6428