#ifndef ATCODER_INTERNAL_QUEUE_HPP
#define ATCODER_INTERNAL_QUEUE_HPP 1

#include <vector>

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

}  // namespace atcoder

#endif  // ATCODER_INTERNAL_QUEUE_HPP


#ifndef ATCODER_MAXFLOW_HPP
#define ATCODER_MAXFLOW_HPP 1

#include <algorithm>
#include <cassert>
#include <limits>
#include <queue>
#include <vector>

namespace atcoder {

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 = [&](int t, Cap up) {
            std::vector<int> st;
            st.push_back(t);
            while (!st.empty()) {
                const int v = st.back();
                if (v == s) {
                    st.pop_back();
                    Cap flow = up;
                    for (auto &w : st) {
                        _edge& e = g[w][iter[w]];
                        flow = std::min(flow, g[e.to][e.rev].cap);
                    }

                    for (auto &w : st) {
                        _edge& e = g[w][iter[w]];
                        e.cap += flow;
                        g[e.to][e.rev].cap -= flow;
                    }
                    st.clear();
                    return flow;
                }
                const int level_v = level[v];
                // NOTE: int& is important here.
                // this is same as
                // for (; iter[v] < int(g[v].size()); ++iter[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;
                    st.push_back(e.to);
                    break;
                }
                if (iter[v] == g[v].size()) {
                    st.pop_back();
                    level[v] = _n; // Make this node unreachable.
                }
            }
            return 0;
        };

        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(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

#endif  // ATCODER_MAXFLOW_HPP


#include <iostream>

using namespace std;
using namespace atcoder;

int main() {
    int n, m;
    cin >> n >> m;

    vector<string> grid(n);
    for (int i = 0; i < n; i++) {
        cin >> grid[i];
    }

    /**
     * generate (s -> even grid -> odd grid -> t) graph
     * grid(i, j) correspond to vertex (i * m + j)
     **/
    mf_graph<int> g(n * m + 2);
    int s = n * m, t = n * m + 1;

    // s -> even / odd -> t
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (grid[i][j] == '#') continue;
            int v = i * m + j;
            if ((i + j) % 2 == 0) {
                g.add_edge(s, v, 1);
            } else {
                g.add_edge(v, t, 1);
            }
        }
    }

    // even -> odd
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if ((i + j) % 2 || grid[i][j] == '#') continue;
            int v0 = i * m + j;
            if (i && grid[i - 1][j] == '.') {
                int v1 = (i - 1) * m + j;
                g.add_edge(v0, v1, 1);
            }
            if (j && grid[i][j - 1] == '.') {
                int v1 = i * m + (j - 1);
                g.add_edge(v0, v1, 1);
            }
            if (i + 1 < n && grid[i + 1][j] == '.') {
                int v1 = (i + 1) * m + j;
                g.add_edge(v0, v1, 1);
            }
            if (j + 1 < m && grid[i][j + 1] == '.') {
                int v1 = i * m + (j + 1);
                g.add_edge(v0, v1, 1);
            }
        }
    }

    cout << g.flow(s, t) << endl;

    auto edges = g.edges();
    for (auto e : edges) {
        if (e.from == s || e.to == t || e.flow == 0) continue;
        int i0 = e.from / m, j0 = e.from % m;
        int i1 = e.to / m, j1 = e.to % m;

        if (i0 == i1 + 1) {
            grid[i1][j1] = 'v';
            grid[i0][j0] = '^';
        } else if (j0 == j1 + 1) {
            grid[i1][j1] = '>'; grid[i0][j0] = '<';
        } else if (i0 == i1 - 1) {
            grid[i0][j0] = 'v';
            grid[i1][j1] = '^';
        } else {
            grid[i0][j0] = '>'; grid[i1][j1] = '<';
        }
    }

    for (int i = 0; i < n; i++) {
        cout << grid[i] << endl;
    }

    return 0;
}



Measured memory_bytes: 5244