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

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << "Line " << __LINE__ << ": " <<  #x << " = " << (x) << "\n";
#define spa << " " <<
#define fi first
#define se second
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()

using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;

template<typename T> using V = vector<T>;
template<typename T> using P = pair<T, T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;

template <class T> void UNIQUE(vector<T> &x) {sort(ALL(x));x.erase(unique(ALL(x)), 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 (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<"\n";}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<"\n";};

const ll INF = (1ll<<62);
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const ll mod = (int)1e9 + 7;
//const ll mod = 998244353;

int main(){

    ll N, M;
    cin >> N >> M;
    V<string> S(N);
    REP(i, N) cin >> S[i];

    auto p2id = [&](ll x, ll y){
        return x*M + y;
    };

    auto id2p = [&](ll idx){
        pll res;
        res.first = idx/M;
        res.second = idx%M;
        return res;
    };

    mf_graph<ll> G(N*M+2);
    ll s = N*M;
    ll t = N*M+1;

    V<ll> dx = {1, 0, -1, 0};
    V<ll> dy = {0, 1, 0, -1};

    REP(i, N){
        REP(j, M){
            if(S[i][j] == '#') continue;
            ll cur = p2id(i, j);
            if((i+j)%2){
                G.add_edge(cur, t, 1);
            }else{
                G.add_edge(s, cur, 1);
                REP(t, 4){
                    ll nx = i + dx[t];
                    ll ny = j + dy[t];
                    if(nx<0 or nx>=N or ny<0 or ny>=M) continue;
                    if(S[nx][ny] == '#') continue;
                    ll next = p2id(nx, ny);
                    G.add_edge(cur, next, 1);
                }
            }
        }
    }
    auto res = G.flow(s, t);

    cout << res << endl;

    for(auto e: G.edges()){
        if(e.from == s or e.to == t) continue;
        if(e.flow == 1){
            auto [px, py] = id2p(e.from);
            auto [qx, qy] = id2p(e.to);
            if(px==qx){
                if(py == qy-1){
                    S[px][py] = '>';
                    S[qx][qy] = '<';
                }else{
                    S[px][py] = '<';
                    S[qx][qy] = '>';
                }
            }else{
                if(px == qx-1){
                    S[px][py] = 'v';
                    S[qx][qy] = '^';
                }else{
                    S[px][py] = '^';
                    S[qx][qy] = 'v';
                }
            }
        }
    }

    REP(i, N){
        cout << S[i] << endl;
    }

    return 0;
}

Measured memory_bytes: 6136