#include <bits/stdc++.h>
using namespace std;
#define repex(i, a, b, c) for(int i = a; i < b; i += c)
#define repx(i, a, b) repex(i, a, b, 1)
#define rep(i, n) repx(i, 0, n)
#define repr(i, a, b) for(int i = a; i >= b; i--)
#define pb push_back
#define a first
#define b second
#define all(x) x.begin(), x.end()

// AtCoder Library(https://img.atcoder.jp/practice2/ac-library.zip)
// -> 一部改変(2020/09/13).
template <class T> struct simple_queue{
    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++; }
};

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.pb({from, int(g[from].size())});
        g[from].pb(_edge{to, int(g[to].size()), cap});
        g[to].pb(_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].a][pos[i].b];
        auto _re = g[_e.to][_e.rev];
        return edge{pos[i].a, _e.to, _e.cap + _re.cap, _re.cap};
    }
    vector<edge> edges(){
        int m = int(pos.size());
        vector<edge> result;
        rep(i, m) result.pb(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].a][pos[i].b];
        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, numeric_limits<Cap>::max());
    }
    Cap flow(int s, int t, Cap flow_limit) {
        assert(0 <= s && s < _n);
        assert(0 <= t && t < _n);
        vector<int> level(_n), iter(_n);
        simple_queue<int> q;
        auto bfs = [&](){
            fill(all(level), -1);
            level[s] = 0;
            q.clear();
            q.push(s);
            while(!q.empty()){
                int v = q.front();
                q.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;
                    q.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, 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;
            fill(all(iter), 0);
            while(flow < flow_limit){
                Cap f = dfs(dfs, t, flow_limit - flow);
                if(!f) break;
                flow += f;
            }
        }
        return flow;
    }
    vector<bool> min_cut(int s){
        vector<bool> visited(_n);
        simple_queue<int> q;
        q.push(s);
        while(!q.empty()){
            int p = q.front();
            q.pop();
            visited[p] = true;
            for(auto e : g[p]){
                if(e.cap && !visited[e.to]){
                    visited[e.to] = true;
                    q.push(e.to);
                }
            }
        }
        return visited;
    }
private:
    int _n;
    struct _edge{
        int to, rev;
        Cap cap;
    };
    vector<pair<int, int>> pos;
    vector<vector<_edge>> g;
};

// maxflow.html を 参照.
int main(){
    
    int n, m;
    scanf("%d %d", &n, &m);
    vector<string> grid;
    rep(i, n){
        char c[111];
        scanf("%s", c);
        string s(c);
        grid.pb(c);
    }
    
    /**
     * 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
    rep(i, n){
        rep(j, m){
            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
    rep(i, n){
        rep(j, m){
            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);
            }
        }
    }
    printf("%d\n", g.flow(s, t));
    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] = '<';
        }
    }
    rep(i, n) printf("%s\n", grid[i].c_str());
    return 0;
    
}

Measured memory_bytes: 5724