/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.09.08 18:51:26
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;


struct Dinic {
private:
    struct edge {
        int to;
        ll cap;
        int rev;
        bool isrev;
        int idx;
    };
    vector< int > min_cost, iter;
    bool bfs(int s, int t) {
        min_cost.assign(graph.size(), -1);
        queue< int > que;
        min_cost[s] = 0;
        que.push(s);
        while (!que.empty() && min_cost[t] == -1) {
            int p = que.front();
            que.pop();
            for (auto &e : graph[p]) {
                if (e.cap > 0 && min_cost[e.to] == -1) {
                    min_cost[e.to] = min_cost[p] + 1;
                    que.push(e.to);
                }
            }
        }
        return min_cost[t] != -1;
    }
    ll dfs(int idx, const int t, ll flow) {
        if (idx == t) return flow;
        for (int &i = iter[idx]; i < graph[idx].size(); i++) {
            edge &e = graph[idx][i];
            if (e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
                ll d = dfs(e.to, t, min(flow, e.cap));
                if (d > 0) {
                    e.cap -= d;
                    graph[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }
public:
    vector< vector< edge > > graph;
    Dinic(int V) : graph(V) {}
    
    void add_edge(int from, int to, ll cap, int idx = -1) {
        graph[from].push_back({to, cap, (int)graph[to].size(), false, idx});
        graph[to].push_back({from, 0, (int)graph[from].size() - 1, true, idx});
    }
    
    ll max_flow(int s, int t) {
        ll flow = 0;
        while (bfs(s, t)) {
            iter.assign(graph.size(), 0);
            ll f = 0;
            while ((f = dfs(s, t, 1e9 + 6)) > 0) flow += f;
        }
        return flow;
    }
    void output() {
        for (int i = 0; i < graph.size(); i++) {
            for (auto &e : graph[i]) {
                if (e.isrev) continue;
                auto &rev_e = graph[e.to][e.rev];
                cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << e.cap + rev_e.cap << ")" << endl;
            }
        }
    }
};
int n, m;
inline pair< int, int > to_zahyo(int x) {
    return make_pair(x / m, x % m);
}
inline int to_id(int x, int y) {
    return x * m + y;
}
inline int color(int x, int y) {
    return (x + y) % 2 == 0 ? 0 : 1;
}
int color(int x) {
    auto p = to_zahyo(x);
    return color(p.first, p.second);
}
int main() {
    cin >> n >> m;
    vector< string > s(n);
    int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
    for (int i = 0; i < n; i++) {
        cin >> s[i];
    }
    Dinic g(n * m + 2);
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (s[i][j] == '#') continue;
            if (color(i, j) == 0) {
                for (int k = 0; k < 4; k++) {
                    int x = i + dx[k], y = j + dy[k];
                    if (x < 0 || x >= n || y < 0 || y >= m || s[x][y] == '#') continue;
                    g.add_edge(to_id(i, j), to_id(x, y), 1);
                }
                g.add_edge(n * m, to_id(i, j), 1);
            } else {
                g.add_edge(to_id(i, j), n * m + 1, 1);
            }
        }
    }
    cout << g.max_flow(n * m, n * m + 1) << endl;
    for (int i = 0; i < g.graph.size(); i++) {
        for (auto &e : g.graph[i]) {
            if (e.isrev) continue;
            auto &rev_e = g.graph[e.to][e.rev];
            if (rev_e.cap == 1 && i != n*m && e.to != n*m+1) {
                auto p1 = to_zahyo(i), p2 = to_zahyo(e.to);
                if (p1.first - p2.first == 1) {
                    s[p1.first][p1.second] = '^';
                    s[p2.first][p2.second] = 'v';
                }
                else if (p1.first - p2.first == -1) {
                    s[p1.first][p1.second] = 'v';
                    s[p2.first][p2.second] = '^';
                }
                else if (p1.second - p2.second == 1) {
                    s[p1.first][p1.second] = '<';
                    s[p2.first][p2.second] = '>';
                }
                else {
                    s[p1.first][p1.second] = '>';
                    s[p2.first][p2.second] = '<';
                }
            } 
        }
    }
    for (int i = 0; i < n; i++) {
        cout << s[i] << endl;
    }
    return 0;
}

Measured memory_bytes: 6416