#include <bits/stdc++.h>
using namespace std;
/*
#include <atcoder/all>
using namespace atcoder;
*/
/*
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using bll = boost::multiprecision::cpp_int;
using bdouble = boost::multiprecision::number<boost::multiprecision::cpp_dec_float<100>>;
using namespace boost::multiprecision;
*/
#ifdef LOCAL_TEST
	#define BOOST_STACKTRACE_USE_ADDR2LINE
	#define BOOST_STACKTRACE_ADDR2LINE_LOCATION /usr/local/opt/binutils/bin/addr2line
	#define _GNU_SOURCE 1
	#include <boost/stacktrace.hpp>
	namespace std {
		template<typename T> class dvector : public std::vector<T> {
		public:
			dvector() : std::vector<T>() {}
			explicit dvector(size_t n, const T& value = T()) : std::vector<T>(n, value) {}
			dvector(const std::vector<T>& v) : std::vector<T>(v) {}
			dvector(const std::initializer_list<T> il) : std::vector<T>(il) {}
			dvector(const std::string::iterator first, const std::string::iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::iterator first, const typename std::vector<T>::iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::reverse_iterator first, const typename std::vector<T>::reverse_iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::const_iterator first, const typename std::vector<T>::const_iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::const_reverse_iterator first, const typename std::vector<T>::const_reverse_iterator last) : std::vector<T>(first, last) {}
			T& operator[](size_t n) {
				try { return this->at(n); } catch (const std::exception& e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; return this->at(n); }
			}
			const T& operator[](size_t n) const {
				try { return this->at(n); } catch (const std::exception& e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; return this->at(n); }
			}
		};
	}
	class dbool {
	private:
		bool boolvalue;
	public:
		dbool() : boolvalue(false) {}
		dbool(bool b) : boolvalue(b) {}
		operator bool&() { return boolvalue; }
		operator const bool&() const { return boolvalue; }
	};
	#define vector dvector
	#define bool dbool
	class SIGFPE_exception : std::exception {};
	class SIGSEGV_exception : std::exception {};
	void catch_SIGFPE([[maybe_unused]] int e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; throw SIGFPE_exception(); }
	void catch_SIGSEGV([[maybe_unused]] int e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; throw SIGSEGV_exception(); }
	signed convertedmain();
	signed main() { signal(SIGFPE, catch_SIGFPE); signal(SIGSEGV, catch_SIGSEGV); return convertedmain(); }
	#define main() convertedmain()
#endif
#ifdef LOCAL_DEV
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::pair<T1, T2>& p) {
		return s << "(" << p.first << ", " << p.second << ")"; }
	template <typename T, size_t N> std::ostream& operator<<(std::ostream& s, const std::array<T, N>& a) {
		s << "{ "; for (size_t i = 0; i < N; ++i){ s << a[i] << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::set<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::multiset<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::map<T1, T2>& m) {
		s << "{\n"; for (auto itr = m.begin(); itr != m.end(); ++itr){ s << "\t" << (*itr).first << " : " << (*itr).second << "\n"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::deque<T>& v) {
		for (size_t i = 0; i < v.size(); ++i){ s << v[i]; if (i < v.size() - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<T>& v) {
		for (size_t i = 0; i < v.size(); ++i){ s << v[i]; if (i < v.size() - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<std::vector<T>>& vv) {
		s << "\\\n"; for (size_t i = 0; i < vv.size(); ++i){ s << vv[i] << "\n"; } return s; }
	void debug_impl() { std::cerr << '\n'; }
	template<typename Head, typename... Tail> void debug_impl(Head head, Tail... tail) { std::cerr << " " << head << (sizeof...(tail) ? "," : ""); debug_impl(tail...); }
	#define debug(...) do { std::cerr << ":" << __LINE__ << " (" << #__VA_ARGS__ << ") ="; debug_impl(__VA_ARGS__); } while (false)
#else
	#define debug(...) do {} while (false)
#endif
//#define int long long
using ll = long long;
//constexpr int INF = (ll)1e9 + 7; //INT_MAX = (1<<31)-1 = 2147483647
constexpr ll INF = (ll)1e18; //(1LL<<63)-1 = 9223372036854775807
//constexpr ll MOD = (ll)1e9 + 7; //primitive root = 5
constexpr ll MOD = 998244353; //primitive root = 3
constexpr double EPS = 1e-9;
constexpr ll dx[4] = {1, 0, -1, 0};
constexpr ll dy[4] = {0, 1, 0, -1};
constexpr ll dx8[8] = {1, 0, -1, 0, 1, 1, -1, -1};
constexpr ll dy8[8] = {0, 1, 0, -1, 1, -1, 1, -1};
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define rrep(i, n)   for(ll i=(n)-1; i>=0; --i)
#define rrepeq(i, n) for(ll i=(n)  ; i>=1; --i)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
void p() { std::cout << '\n'; }
template<typename Head, typename... Tail> void p(Head head, Tail... tail) { std::cout << head << (sizeof...(tail) ? " " : ""); p(tail...); }
template<typename T> inline void pv(std::vector<T>& v) { for(ll i=0, N=v.size(); i<N; i++) std::cout << v[i] << " \n"[i==N-1]; }
template<typename T> inline bool chmax(T& a, T b) { return a < b && (a = b, true); }
template<typename T> inline bool chmin(T& a, T b) { return a > b && (a = b, true); }
template<typename T> inline void uniq(std::vector<T>& v) { v.erase(std::unique(v.begin(), v.end()), v.end()); }

/*-----8<-----template-----8<-----*/

::std::vector<::std::pair<ll, ll>> gabow_edmonds(const ::std::vector<::std::vector<ll>>& gra){
	struct edge {
		ll to;
		ll label;
		edge(ll to, ll label) : to(to), label(label) {}
	};
	// E0 - 初期化
	ll N = gra.size();
	::std::vector<::std::vector<edge>> g(N + 1);
	::std::vector<::std::pair<ll, ll>> edges;
	{
		ll cnt = N + 1;
		for(ll i = 0;i < N;i++){
			for(auto to : gra[i]){
				if(i < to){
					g[to + 1].emplace_back(i + 1, cnt);
					g[i + 1].emplace_back(to + 1, cnt++);
					edges.emplace_back(i + 1, to + 1);
				}
			}
		}
	}
	::std::vector<ll> mate(N + 1 , 0);
	::std::vector<ll> label(N + 1 , -1);
	::std::vector<ll> first(N + 1 , 0);
	::std::queue<ll> que;

	// firstの遅延評価
	::std::function<ll(ll)> eval_first = [&](ll x){
		if(label[first[x]] < 0) return first[x];
		first[x] = eval_first(first[x]);
		return first[x];
	};

	// サブルーチンR
	::std::function<void(ll, ll)> rematch = [&](ll v, ll w){
		// R1
		ll t = mate[v];
		mate[v] = w;
		if(mate[t] != v) return;
		// R2
		if(label[v] <= N){
			mate[t] = label[v];
			rematch(label[v] , t);
		}
		// R3
		else{
			ll x = edges[label[v] - N - 1].first;
			ll y = edges[label[v] - N - 1].second;
			rematch(x , y);
			rematch(y , x);
		}
	};

	::std::function<void(ll, ll, ll)> assignLabel = [&](ll x, ll y, ll num){
		// L0
		ll r = eval_first(x);
		ll s = eval_first(y);
		ll join = 0;
		if(r == s) return;
		// -numがフラグ
		label[r] = -num;
		label[s] = -num;
		while(true){
			// L1
			if(s != 0) ::std::swap(r , s);
			// L2
			r = eval_first(label[mate[r]]);
			if(label[r] == -num){
				join = r;
				break;
			}
			label[r] = -num;
		}
		// L3
		ll v = first[x];
		// L4
		while(v != join){
			que.push(v);
			label[v] = num;
			first[v] = join;
			v = first[label[mate[v]]];
		}
		// L3
		v = first[y];
		// L4
		while(v != join){
			que.push(v);
			label[v] = num;
			first[v] = join;
			v = first[label[mate[v]]];
		}
		// L5は遅延評価しているため不要
		// L6
		return;
	};

	::std::function<bool(ll)> augment_check = [&](ll u){
		// E1 後半
		first[u] = 0;
		label[u] = 0;
		que.push(u);
		while(!que.empty()){
			// E2 
			ll x = que.front();
			que.pop();
			for(auto e : g[x]){
				ll y = e.to;
				// E3
				if(mate[y] == 0 && y != u){
					mate[y] = x;
					rematch(x , y);
					return true;
				}
				// E4
				else if(label[y] >= 0){
					assignLabel(x , y , e.label);
				}
				// E5
				else if(label[mate[y]] < 0){
					label[mate[y]] = x;
					first[mate[y]] = y;
					que.push(mate[y]);
				}
				// E6
			}
		}
		return false;
	};

	for(ll i = 1;i <= N;i++){
		// E1
		que = ::std::queue<ll>();
		if(mate[i] != 0) continue;
		if(augment_check(i)){
			// E7
			::std::fill(label.begin(), label.end(), -1);
		}
	}

	::std::vector<::std::pair<ll, ll>> ans;
	for(ll i = 1;i <= N;i++){
		if(i < mate[i]){
			ans.emplace_back(i-1 , mate[i]-1);
		}
	}
	return ans;
}

/*-----8<-----library-----8<-----*/

void solve() {
	ll H,W;
	cin>>H>>W;
	vector<string> a(H);
	rep(i,H)cin>>a[i];

	vector<vector<ll>> g(H*W);
	rep(i,H)rep(j,W){
		if(a[i][j]=='#')continue;
		rep(k, 4) {
			ll nx = dx[k] + i;
			ll ny = dy[k] + j;
			if(nx <= -1 || ny <= -1 || nx >= H || ny >= W) continue;
			if(a[nx][ny] == '#') continue;
			g[i*W+j].push_back(nx*W+ny);
		}
	}

	vector<pair<ll,ll>> pairv = gabow_edmonds(g);
	for(auto&& pr:pairv){
		if(pr.first>pr.second)swap(pr.first,pr.second);
		ll x1=pr.first/W;
		ll y1=pr.first%W;
		ll x2=pr.second/W;
		ll y2=pr.second%W;
		if(x1==x2){
			a[x1][y1]='>';
			a[x2][y2]='<';
		}else{
			a[x1][y1]='v';
			a[x2][y2]='^';
		}
	}
	p(pairv.size());
	rep(i,H)p(a[i]);
}

signed main() {
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);
	//ll Q; cin >> Q; while(Q--)solve();
	solve();
	return 0;
}


Measured memory_bytes: 5640