#include <bits/stdc++.h>
using namespace std;

template <typename flow_t>
struct Dinic {
    const flow_t INF;

    struct edge {
        int to;
        flow_t cap;
        int rev;
        bool isrev;
        int idx;
    };

    vector<vector<edge> > graph;
    vector<int> min_cost, iter;

    explicit Dinic(int V) : INF(numeric_limits<flow_t>::max()), graph(V) {}

    void add_edge(int from, int to, flow_t cap, int idx = -1) {
        graph[from].emplace_back(
            (edge){to, cap, (int)graph[to].size(), false, idx});
        graph[to].emplace_back(
            (edge){from, 0, (int)graph[from].size() - 1, true, idx});
    }

    bool build_augment_path(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;
    }

    flow_t find_min_dist_augment_path(int idx, const int t, flow_t 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]) {
                flow_t d =
                    find_min_dist_augment_path(e.to, t, min(flow, e.cap));
                if (d > 0) {
                    e.cap -= d;
                    graph[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }

    flow_t max_flow(int s, int t) {
        flow_t flow = 0;
        while (build_augment_path(s, t)) {
            iter.assign(graph.size(), 0);
            flow_t f;
            while ((f = find_min_dist_augment_path(s, t, INF)) > 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;
            }
        }
    }

    struct edge_info {
        int from, to;
        flow_t flow, cap;
    };

    vector<edge_info> edges() {
        vector<edge_info> res;
        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];
                res.push_back(edge_info{i, e.to, rev_e.cap, e.cap + rev_e.cap});
            }
        }
        return res;
    }
};

#define for_range(i, a, b) for (int i = (a); i < (b); i++)

int main() {
    int h, w;
    cin >> h >> w;
    vector<string> grid(h);
    for (auto &row : grid) cin >> row;

    Dinic<int> gr(h * w + 2);
    auto id = [&](int i, int j) { return i * w + j; };
    int start = id(h, 0), goal = id(h, 1);
    for_range(i, 0, h) for_range(j, 0, w) {
        if (grid[i][j] == '#') continue;
        if (i % 2 == j % 2) {
            gr.add_edge(id(i, j), goal, 1);
            continue;
        }
        gr.add_edge(start, id(i, j), 1);
        const int DX[] = {1, 0, -1, 0};
        const int DY[] = {0, 1, 0, -1};
        for_range(k, 0, 4) {
            int x = i + DX[k], y = j + DY[k];
            if (x < 0 || h <= x || y < 0 || w <= y) continue;
            if (grid[x][y] == '#') continue;
            gr.add_edge(id(i, j), id(x, y), 1);
        }
    }

    int flow = gr.max_flow(start, goal);
    auto edge = gr.edges();
    vector<string> ans(grid);

    for (auto e : edge) {
        if (e.from == start || e.to == goal || e.flow == 0) continue;
        auto id_r = [&](int x) { return pair<int, int>{x / w, x % w}; };
        auto a = id_r(e.from), b = id_r(e.to);
        if (a > b) swap(a, b);
        if (a.first + 1 == b.first) {
            ans[a.first][a.second] = 'v';
            ans[b.first][b.second] = '^';
        } else {
            ans[a.first][a.second] = '>';
            ans[b.first][b.second] = '<';
        }
    }

    cout << flow << '\n';
    for (auto row : ans) cout << row << '\n';
}

Measured memory_bytes: 6036