//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0xccccccc;
const ll LINF = 0xcccccccccccccccLL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}

struct edge{
	int to, rev;
	int64_t cap;
	edge(int t=0, int64_t c=0, int r=0):to(t), cap(c), rev(r) {}
};

struct max_flow {
	vector<vector<edge> > G;
	vector<int> level, iter;
	int n;
	max_flow(int n=0):n(n), G(n), level(n), iter(n) {}
	inline int add(int from, int to, int64_t cap) {
		G[from].emplace_back(to, cap, G[to].size());
		G[to].emplace_back(from, 0, G[from].size()-1);
		return G[from].size()-1;
	}
	void bfs(int s) {
		for(int i = 0; i < n; i++) level[i] = -1;
		queue<int> que;
		level[s] = 0;
		que.emplace(s);
		while(!que.empty()) {
			int now = que.front();
			que.pop();
			for(edge &e:G[now]) {
				if(e.cap > 0 and level[e.to] < 0) {
					level[e.to] = level[now] + 1;
					que.emplace(e.to);
				}
			}
		}
	}
	int64_t dfs(int v, int t, int64_t f) {
		if(v == t) return f;
		for(int &i = iter[v]; i < G[v].size(); i++) {
			edge &e = G[v][i];
			if(e.cap > 0 and level[v] < level[e.to]) {
				int64_t d = dfs(e.to, t, min(f, e.cap));
				if(d > 0) {
					e.cap -= d;
					G[e.to][e.rev].cap += d;
					return d;
				}
			}
		}
		return 0;
	}
	int64_t Dinic(int s, int t) {
		int64_t flow = 0;
		while(true) {
			bfs(s);
			if(level[t] < 0) return flow;
			for(int i = 0; i < n; i++) iter[i] = 0;
			int64_t f;
			while((f = dfs(s, t, INT64_MAX)) > 0) flow += f;
		}
	}
};

//head

int n, m;
max_flow mfl(10100);
string s[110];

inline int num(int i, int j) {return i*m+j;}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n >> m;
	rep(i, n) cin >> s[i];
	const int ss = n*m, tt = ss+1;
	rep(i, n) rep(j, m) {
		if(i and s[i-1][j] == '.' and s[i][j] == '.') {
			if((i+j)&1) mfl.add(num(i-1, j), num(i, j), 1);
			else mfl.add(num(i, j), num(i-1, j), 1);
		}
		if(j and s[i][j-1] == '.' and s[i][j] == '.') {
			if((i+j)&1) mfl.add(num(i, j-1), num(i, j), 1);
			else mfl.add(num(i, j), num(i, j-1), 1);
		}
		if((i+j)&1) mfl.add(num(i, j), tt, 1);
		else mfl.add(ss, num(i, j), 1);
	}
	cout << mfl.Dinic(ss, tt) << endl;
	rep(i, n) rep(j, m) {
		if(~(i+j)&1) {
			for(edge &e:mfl.G[num(i, j)]) {
				if(e.cap) continue;
				if(e.to == ss) continue;
				int ne = e.to;
				int ni = ne/m, nj = ne%m;
				int ui = i, uj = j;
				if(ni == ui) {
					if(nj > uj) swap(nj, uj);
					s[i][nj] = '>';
					s[i][uj] = '<';
				}
				else {
					if(ni > ui) swap(ni, ui);
					s[ni][j] = 'v';
					s[ui][j] = '^';
				}
			}
		}
	}
	rep(i, n) cout << s[i] << '\n';
}

Measured memory_bytes: 5228