#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
using namespace std;
typedef long long ll;
const int INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;
template <class T>
void get_unique(vector<T>& x) {
    x.erase(unique(x.begin(), x.end()), x.end());
}
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T>
ostream& operator<<(ostream& os, vector<T> v) {
    for (int i = 0; i < sz(v); i++) {
        os << v[i];
        if (i < sz(v) - 1) os << " ";
    }
    return os;
}
namespace maxflow {
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 maxflow
int main() {
    int n, m;
    cin >> n >> m;
    vector<string> v(n);
    rep(i, n) cin >> v[i];
    maxflow::mf_graph<int> g(n * m + 2);
    auto id = [&](int i, int j) { return i * m + j; };
    auto y = [&](int id) { return id / m; };
    auto x = [&](int id) { return id % m; };

    int s = n * m, t = s + 1;
    rep(i, n) rep(j, m) {
        if (v[i][j] == '#') continue;
        if (i + 1 < n && v[i + 1][j] == '.') {
            if (i + j & 1) {
                g.add_edge(id(i, j), id(i + 1, j), 1);
            } else {
                g.add_edge(id(i + 1, j), id(i, j), 1);
            }
        }
        if (j + 1 < m && v[i][j + 1] == '.') {
            if (i + j & 1) {
                g.add_edge(id(i, j), id(i, j + 1), 1);
            } else {
                g.add_edge(id(i, j + 1), id(i, j), 1);
            }
        }
        if (i + j & 1) {
            g.add_edge(s, id(i, j), 1);
        } else {
            g.add_edge(id(i, j), t, 1);
        }
    }
    cout << g.flow(s, t) << '\n';
    for (auto [from, to, cap, flow] : g.edges()) {
        if (from == s || to == t) continue;
        if (flow == 0) continue;
        if (from > to) swap(from, to);
        if (from + m == to) {
            v[y(from)][x(from)] = 'v';
            v[y(to)][x(to)] = '^';
        } else {
            v[y(from)][x(from)] = '>';
            v[y(to)][x(to)] = '<';
        }
    }
    rep(i, n) cout << v[i] << '\n';
}


Measured memory_bytes: 5520