#include<bits/stdc++.h>
typedef long long ll;
typedef std::pair<ll,ll> P;

#define rep(i,n) for(int i = 0; i < int(n); i++)
using namespace std;



template<class T> inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }

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;
};

int main() {
	int n, m;
    cin >> n >> m;
    mf_graph<ll> g(n * m + 2);
    vector<int> grid(n * m, 0);
    vector<string> ts(n);
    rep(i, n) {
        string s;
        cin >> s;
        ts[i] = s;
        rep(j, m) {
            int id = i * m + j;
            grid[id] = s[j] == '.';
        }
    }
    rep(i, n) {
        rep(j, m) {
            int id = i * m + j;
            if (!grid[id]) continue;
            if ((i+j) % 2 == 1) {
                g.add_edge(id, n * m + 1, 1);
                continue;
            }
            g.add_edge(n * m, id, 1);
            if (i > 0) {
                int nid = (i - 1) * m + j;
                if (grid[nid]) {
                    g.add_edge(id, nid, 1);
                }
            }
            if (i < n - 1) {
                int nid = (i + 1) * m + j;
                if (grid[nid]) {
                    g.add_edge(id, nid, 1);
                }
            }
            if (j  > 0) {
                int nid = i * m + j - 1;
                if (grid[nid]) {
                    g.add_edge(id, nid, 1);
                }
            }
            if (j < m-1) {
                int nid = i*m + j + 1;
                if (grid[nid]) {
                    g.add_edge(id, nid, 1);
                }
            }
        }
    }
    auto f = g.flow(n* m, n* m + 1);
    auto e = g.edges();
    for (auto edge : e) {
        auto a = edge.from;
        auto b = edge.to;
        if (a >= n * m || b >= n * m)continue;
        if (edge.flow <= 0) continue;
        int x1 = a % m;
        int y1 = a / m;
        int x2 = b % m;
        int y2 = b / m;
        if (x1 == x2) {
            if (y1 > y2) {
                swap(y1, y2);
            }
            ts[y1][x1] = 'v';
            ts[y2][x1] = '^';
        }
        else {
            if (x1 > x2) {
                swap(x1, x2);
            }
            ts[y1][x1] = '>';
            ts[y2][x2] = '<';
        }
    }
    cout << f << endl;
    rep(i, n) {
        cout << ts[i] << endl;
    }
	return 0;
}


Measured memory_bytes: 6208