#include <bits/stdc++.h>
using namespace std;
using ll = long long; using pii = pair<int, int>; using vi = vector<int>; using vvi = vector<vi>; using vl = vector<ll>; using vvl = vector<vl>;
#define rep(CNT, GOAL) for (int CNT = 0; CNT < (int)(GOAL); CNT++)
#define rep2(CNT, START, GOAL) for (int CNT = (int)(START); CNT < (int)(GOAL); CNT++)
#define rep3(CNT, START, GOAL) for (int CNT = (int)(START); CNT > (int)(GOAL); CNT--)
#define all(CONT) begin(CONT), end(CONT)

namespace atcoder {

namespace internal {

template <class T> struct simple_queue {
    std::vector<T> payload;
    int pos = 0;
    void reserve(int n) { payload.reserve(n); }
    int size() const { return int(payload.size()) - pos; }
    bool empty() const { return pos == int(payload.size()); }
    void push(const T& t) { payload.push_back(t); }
    T& front() { return payload[pos]; }
    void clear() {
        payload.clear();
        pos = 0;
    }
    void pop() { pos++; }
};

}  // namespace internal

template <class Cap> struct mf_graph {
  public:
    mf_graph() : _n(0) {}
    mf_graph(int n) : _n(n), g(n) {}

    int add_edge(int from, int to, Cap cap) {
        assert(0 <= from && from < _n);
        assert(0 <= to && to < _n);
        assert(0 <= cap);
        int m = int(pos.size());
        pos.push_back({from, int(g[from].size())});
        g[from].push_back(_edge{to, int(g[to].size()), cap});
        g[to].push_back(_edge{from, int(g[from].size()) - 1, 0});
        return m;
    }

    struct edge {
        int from, to;
        Cap cap, flow;
    };

    edge get_edge(int i) {
        int m = int(pos.size());
        assert(0 <= i && i < m);
        auto _e = g[pos[i].first][pos[i].second];
        auto _re = g[_e.to][_e.rev];
        return edge{pos[i].first, _e.to, _e.cap + _re.cap, _re.cap};
    }
    std::vector<edge> edges() {
        int m = int(pos.size());
        std::vector<edge> result;
        for (int i = 0; i < m; i++) {
            result.push_back(get_edge(i));
        }
        return result;
    }
    void change_edge(int i, Cap new_cap, Cap new_flow) {
        int m = int(pos.size());
        assert(0 <= i && i < m);
        assert(0 <= new_flow && new_flow <= new_cap);
        auto& _e = g[pos[i].first][pos[i].second];
        auto& _re = g[_e.to][_e.rev];
        _e.cap = new_cap - new_flow;
        _re.cap = new_flow;
    }

    Cap flow(int s, int t) {
        return flow(s, t, std::numeric_limits<Cap>::max());
    }
    Cap flow(int s, int t, Cap flow_limit) {
        assert(0 <= s && s < _n);
        assert(0 <= t && t < _n);

        std::vector<int> level(_n), iter(_n);
        internal::simple_queue<int> que;

        auto bfs = [&]() {
            std::fill(level.begin(), level.end(), -1);
            level[s] = 0;
            que.clear();
            que.push(s);
            while (!que.empty()) {
                int v = que.front();
                que.pop();
                for (auto e : g[v]) {
                    if (e.cap == 0 || level[e.to] >= 0) continue;
                    level[e.to] = level[v] + 1;
                    if (e.to == t) return;
                    que.push(e.to);
                }
            }
        };
        auto dfs = [&](auto self, int v, Cap up) {
            if (v == s) return up;
            Cap res = 0;
            int level_v = level[v];
            for (int& i = iter[v]; i < int(g[v].size()); i++) {
                _edge& e = g[v][i];
                if (level_v <= level[e.to] || g[e.to][e.rev].cap == 0) continue;
                Cap d =
                    self(self, e.to, std::min(up - res, g[e.to][e.rev].cap));
                if (d <= 0) continue;
                g[v][i].cap += d;
                g[e.to][e.rev].cap -= d;
                res += d;
                if (res == up) break;
            }
            return res;
        };

        Cap flow = 0;
        while (flow < flow_limit) {
            bfs();
            if (level[t] == -1) break;
            std::fill(iter.begin(), iter.end(), 0);
            while (flow < flow_limit) {
                Cap f = dfs(dfs, t, flow_limit - flow);
                if (!f) break;
                flow += f;
            }
        }
        return flow;
    }

    std::vector<bool> min_cut(int s) {
        std::vector<bool> visited(_n);
        internal::simple_queue<int> que;
        que.push(s);
        while (!que.empty()) {
            int p = que.front();
            que.pop();
            visited[p] = true;
            for (auto e : g[p]) {
                if (e.cap && !visited[e.to]) {
                    visited[e.to] = true;
                    que.push(e.to);
                }
            }
        }
        return visited;
    }

  private:
    int _n;
    struct _edge {
        int to, rev;
        Cap cap;
    };
    std::vector<std::pair<int, int>> pos;
    std::vector<std::vector<_edge>> g;
};

}  // namespace atcoder
using namespace atcoder;

template <typename T> void CERR(const T &ELEM) { cerr << ELEM; }
#define dbl(OBJ) cerr << #OBJ << ": "; CERR(OBJ); cerr << "\n"

template <typename T, typename ...Ts> void CERR(const T &FIRST, const Ts &...REST) { CERR(FIRST); cerr << ", "; CERR(REST...); }
#define dbs(...) cerr << "(" << #__VA_ARGS__ << "): ("; CERR(__VA_ARGS__); cerr << ")\n"

// 頂点(i,j)(0<=i<N,0<=j<M)を整数 i*M+j で表す
// N*M(from)->{(i,j)|(i+j)mod2=0}->{(i,j)|(i+j)mod2=1}->N*M+1(to)

vi di = { 1, 0, -1, 0 }, dj = { 0, 1, 0, -1 };

int main() {
	int N, M; cin >> N >> M;
	vector<string> S(N); rep(i, N) cin >> S[i];
	mf_graph<int> g(N * M + 2);
	rep(i, N) rep(j, M) {
		if (S[i][j] == '#') continue;
		if ((i + j) % 2 == 0) {
			g.add_edge(N * M, i * M + j, 1);
			rep (dir, 4) {
				int ni = i + di[dir], nj = j + dj[dir];
				if (ni < 0 or N <= ni or nj < 0 or M <= nj) continue;
				if (S[ni][nj] == '.') g.add_edge(i * M + j, ni * M + nj, 1);
			}
		} else {
			g.add_edge(i * M + j, N * M + 1, 1);
		}
	}

	cout << g.flow(N * M, N * M + 1) << endl;
	vector<string> T = S;

	for (auto e : g.edges()) {
		if (e.from == N * M or e.to == N * M + 1) continue;
		if (e.flow == 0) continue;
		int i = e.from / M, j = e.from % M;
		int ni = e.to / M, nj = e.to % M;
		// dbs(e.from, e.to, e.cap, e.flow); dbs(i, j, ni, nj);

		if (i == ni) {
			if (j < nj) {
				T[i][j] = '>';
				T[i][nj] = '<';
			} else if (nj < j) {
				T[i][nj] = '>';
				T[i][j] = '<';
			}
		} else if (j == nj) {
			if (i < ni) {
				T[i][j] = 'v';
				T[ni][j] = '^';
			} else if (ni < i) {
				T[ni][j] = 'v';
				T[i][j] = '^';
			}
		}
	}
	rep(i, N) cout << T[i] << endl;
}


Measured memory_bytes: 5448