#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <string.h>
#include <cstdio>
#include <tuple>
#include <numeric>
#include <functional>
#include <atcoder/all>
using namespace std; using namespace atcoder;
using ll = long long; using ld = long double;  using pll = pair<ll, ll>;
using vl = vector<ll>; using vll = vector<vl>; using vlll = vector<vll>; using vpll = vector<pll>;
using vs = vector<string>; using tll = tuple<ll, ll, ll>; using vtll = vector<tll>;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
const ld PI = 3.1415926535897932;
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define co(i) cout << i << endl;
#define co2(i,j) cout << i << " " << j << endl;
#define co3(i) cout << i << " ";
#define po(i) cout << i.first << " " << i.second << endl;
void in() {}
void debug_out() { cerr << endl; }
template<typename Head, typename... Tail>
void debug_out(Head h, Tail... t) {
	cerr << " " << h;
	if (sizeof...(t) > 0) cerr << " :";
	debug_out(t...);
}
template <typename T>
ostream& operator<<(ostream& os, vector<T> vec) {
	for (size_t i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
	return os;
}
ll ctoi(char c) {
	switch (c) {
	case '0': return 0; case '1': return 1; case '2': return 2;
	case '3': return 3; case '4': return 4; case '5': return 5;
	case '6': return 6; case '7': return 7; case '8': return 8;
	case '9': return 9;  default: return 0;
	}
}
bool pairCompare(const pll firstElof, pll secondElof)
{
	return firstElof.second < secondElof.second;
}
//**Snippetリスト**//
//rep, vin, all, iteLoop, bitSearch, bitList, nod, LIS, digitDP, treeDP, Rerooting//
//gcdlcm, isPrime, eratos, primeFactorize, Npow, combination, divisor, modinv, doubling//
//dfs, bfs, dijkstra, WarshallFloyd, BellmanFord, UnionFind, Kruskal, RMQ, LCA, FordFulkerson//
ll i, j, k, l; ll N, M, K, H, W, L, X, Y, Z, R, Q, T;
ll MOD = 1000000007, INF = 1LL << 60, ans = 0, z = 0, o = 1;
vll flag, D; vector<vpll> path; vs S;
int main() {
	cin >> N >> M;
	vs S(N);
	for (i = 0; i < N; i++) cin >> S[i];
	mf_graph<ll> G(N * M + 2);
	ll s = N * M; //始点
	ll t = N * M + 1; //終点
	for (i = 0; i < N; i++) {
		for (j = 0; j < M; j++) {
			if (S[i][j] == '#') continue;
			ll v = i * M + j;
			if ((i + j) % 2 == 0) G.add_edge(s, v, 1);
			else G.add_edge(v, t, 1);
		}
	}
	for (i = 0; i < N; i++) {
		for (j = 0; j < M; j++) {
			if ((i + j) % 2 == 1 || S[i][j] == '#') continue;
			ll v0 = i * M + j;
			if (i>0 && S[i - 1][j] == '.') {
				ll v1 = (i - 1) * M + j;
				G.add_edge(v0, v1, 1);
			}
			if (j>0 && S[i][j-1] == '.') {
				ll v1 = i * M + (j-1);
				G.add_edge(v0, v1, 1);
			}
			if (i+1<N && S[i + 1][j] == '.') {
				ll v1 = (i + 1) * M + j;
				G.add_edge(v0, v1, 1);
			}
			if (j+1<M && S[i][j + 1] == '.') {
				ll v1 = i * M + (j + 1);
				G.add_edge(v0, v1, 1);
			}
		}
	}
	cout << G.flow(s, t) << endl;
	auto E = G.edges();
	for (auto e : E) {
		if (e.from == s || e.to == t || e.flow == 0) continue;
		ll i0 = e.from / M, j0 = e.from % M; //元のマスの座標を算出(始点側)
		ll i1 = e.to / M, j1 = e.to % M; //元のマスの座標を算出(終点側)
		// 縦型
		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] = '<';
		}
	}
	for (i = 0; i < N; i++) {
		co(S[i]);
	}
}

Measured memory_bytes: 6236