#include <bits/stdc++.h>
using namespace std;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define REP(i, n) FOR(i,0,n)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define IREP(i, n) IFOR(i,0,n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(),v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x) distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL<<(n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v) { cout << #v << "=" << endl; REP(i_debug, v.size()){ cout << v[i_debug] << ","; } cout << endl; }
#define mdebug(m) { cout << #m << "=" << endl; REP(i_debug, m.size()){ REP(j_debug, m[i_debug].size()){ cout << m[i_debug][j_debug] << ","; } cout << endl;} }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for (auto &x : v) is >> x; return is; }
template<typename T> ostream &operator<<(ostream &os, vector<T> &v){ for(int i = 0; i < v.size(); i++) { cout << v[i]; if(i != v.size() - 1) cout << endl; }; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p){ cout << '(' << p.first << ',' << p.second << ')'; return os; }
template<typename T> void Out(T x) { cout << x << endl; }
template<typename T1, typename T2> void chOut(bool f, T1 y, T2 n) { if(f) Out(y); else Out(n); }

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;

//int dx[4] = {1,0,-1,0};
//int dy[4] = {0,1,0,-1};
//char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
//const int mod = 998244353;

struct edge { int to, cap, rev, id; };

class Graph
{
public:
    int N;
    vector<vector<edge>> G;
    vector<int> level, iter;

    Graph(int N): N(N){
        G = vector<vector<edge>>(N, vector<edge>(0));
        level = vector<int>(N);
        iter = vector<int>(N);
    }

    //実際の流量を求めたい辺には0以上のidを与える　逆辺のcapを用いる
    void add_Directed_edge(int from, int to, int cap, int id = -1){
        G[from].push_back((edge){to, cap, (int)G[to].size(), -1});
        G[to].push_back((edge){from, 0, (int)G[from].size() - 1, id});
    }

    void bfs(int s){
        memset(&level[0], -1, sizeof(level[0]) * level.size());
        queue<int> que;
        level[s] = 0;
        que.push(s);
        while(!que.empty()){
            int v = que.front(); que.pop();
            REP(i, G[v].size()){
                edge &e = G[v][i];
                if(e.cap > 0 && level[e.to] < 0){
                    level[e.to] = level[v] + 1;
                    que.push(e.to);
                }
            }
        }
    }

    int dfs(int v, int t, int f){
        if(v == t) return f;
        for(int &i = iter[v]; i < G[v].size(); i++){
            edge &e = G[v][i];
            if(e.cap > 0 && level[v] < level[e.to]){
                int d = dfs(e.to, t, min(f, e.cap));
                if(d > 0){
                    e.cap -= d;
                    G[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }

    //sからtへのmax flowを求める　flow_limitを設定したらそこで打ち切り
    int max_flow(int s, int t, int flow_limit = -1){
        int flow = 0;
        for(;;){
            bfs(s);
            if(level[t] < 0) return flow;
            memset(&iter[0], 0, sizeof(iter[0]) * iter.size());
            int f;
            while((f = dfs(s, t, INF)) > 0){
                flow += f;
                if(flow_limit >= 0 && flow >= flow_limit) return flow_limit;
            }
        }
    }

    //実際の流量を求める、max_flow(s, t)を使ってから
    vector<int> calc_flow(int num_id){
        vector<int> flow(num_id, 0);
        REP(v, N) for(auto e: G[v]) if(e.id >= 0) flow[e.id] = e.cap;
        return flow;
    }

    void dfs_for_calc_min_cut(int v, vector<bool> &belong2s){
        belong2s[v] = true;
        for(edge e: G[v]) if(e.cap > 0 && !belong2s[e.to]) dfs_for_calc_min_cut(e.to, belong2s);
    }

    //残余グラフでsから到達可能か求める、max_flow(s, t)を使ってから
    vector<bool> min_cut(int s){
        vector<bool> belong2s(N);
        dfs_for_calc_min_cut(s, belong2s);
        return belong2s;
    }

};

signed main(){

    int N, M; cin >> N >> M;
    vector<string> S(N); cin >> S;

    Graph G(N * M + 2);
    int s = N * M, t = s + 1;

    REP(i, N) REP(j, M) if(S[i][j] == '.'){
        if((i + j) % 2 == 0) G.add_Directed_edge(s, i * M + j, 1);
        else G.add_Directed_edge(i * M + j, t, 1);
    }

    int n = 0;
    v_Pii p;
    v_bool h;
    REP(i, N) REP(j, M){
        if(i + 1 < N){
            if((i + j) % 2 == 0) G.add_Directed_edge(i * M + j, (i + 1) * M + j, 1, n);
            else G.add_Directed_edge((i + 1) * M + j, i * M + j, 1, n);
            p.pb(Pii(i, j)); h.pb(true); n++;
        }
        if(j + 1 < M){
            if((i + j) % 2 == 0) G.add_Directed_edge(i * M + j, i * M + j + 1, 1, n);
            else G.add_Directed_edge(i * M + j + 1, i * M + j, 1, n);
            p.pb(Pii(i, j)); h.pb(false); n++;
        }
    }

    int f = G.max_flow(s, t);
    Out(f);

    vec F = G.calc_flow(n);
    REP(k, n) if(F[k] > 0){
        int i = p[k].fi, j = p[k].se;
        if(h[k]){
            S[i][j] = 'v'; S[i + 1][j] = '^';
        }else{
            S[i][j] = '>'; S[i][j + 1] = '<';
        }
    }
    Out(S);

    return 0;
}


Measured memory_bytes: 7152