#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <array>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
#include <bitset>
#include <tuple>
#include <cmath>
#include <complex>
#include <algorithm>
#include <utility>
#include <regex>
#include <cstdint>
#include <numeric>
#include <functional>
#include <cassert>

using namespace std;
#include <atcoder/all>

namespace utils{
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
    ///----- aliases
    using ll = long long int;
    using ull = unsigned long long;

    template<class T, class Compare> using p_queue = priority_queue<T, vector<T>, Compare>;
    template<class T> using min_queue = p_queue<T, greater<T>>;
    template<class T> using max_queue = p_queue<T, less<T>>;

    template<class T> inline bool CHMIN(T& X, const T& A){ if(X > A) {X = A; return true;} return false; }
    template<class T> inline bool CHMAX(T& X, const T& A){ if(X < A) {X = A; return true;} return false; }

    ///----- vector I/O
    template<class T>
    vector<T> VEC(size_t n, T t){
        return vector<T>(n, t);
    }

    template<class ...Ts>
    auto VEC(size_t n, Ts ... ts){
        return vector<decltype(VEC(ts...))>(n, VEC(ts...));
    }


    template<class T>
    istream& operator>>(istream& is, vector<T>& v){
        for (auto &&x : v) { is >> x; } return is;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<T>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << ' ' << *p++;
        }
        return os ;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<vector<T>>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << '\n' << *p++;
        }
        return os;
    }

    ///----- tuple I/O
    template <class S, class T>
    istream& operator>>(istream& is, tuple<S, T>& t){
        return is >> get<0>(t) >> get<1>(t);
    }

    template <class S, class T>
    istream& operator>>(istream& is, pair<S, T>& t){
        return is >> get<0>(t) >> get<1>(t);
    }

    template <class S, class T, class U>
    istream& operator>>(istream& is, tuple<S, T, U>& t){
        return is >> get<0>(t) >> get<1>(t) >> get<2>(t);
    }

    template <class S, class T>
    ostream& operator<<(ostream& os, const tuple<S, T>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t);
    }

    template <class S, class T>
    ostream& operator<<(ostream& os, const pair<S, T>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t);
    }

    template <class S, class T, class U>
    ostream& operator<<(ostream& os, const tuple<S, T, U>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t) << ' ' <<  get<2>(t);
    }

    ///----- constants
    constexpr ll INFLL   = 1'000'000'000'000'000'020ll;
    constexpr ll INF     = 1'000'000'009;
    constexpr double PI      = 3.14'159'265'358'979'323'846;
    constexpr double EPS     = 1e-12;
}
using namespace utils;

class solver{
    istream& is;
    ostream& os;

public:
    solver(istream& I, ostream& O) :is(I), os(O) {}

    int N, M;
    vector<string> S;
    bool input() {
        is >> N >> M;
        S.resize(N);
        for (int i = 0; i < N; ++i) {
            is >> S[i];
        } // end i
        return !!is;
    }

    int d(int x, int y){
        return x*M + y;
    }

    pair<int, int> rd(int x){
        return {x/M, x%M};
    }

    void run();
};

void solver::run(){
    if(!input()) return;
    atcoder::mf_graph<int> G(N*M +2);
    int s = N*M, t = s+1;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            if((i+j)%2) {
                G.add_edge(d(i, j), t, 1);
                continue;
            }
            else G.add_edge(s, d(i, j), 1);
            if(S[i][j] == '#') continue;
            if(j+1 < M and S[i][j+1] == '.'){
                G.add_edge(d(i, j), d(i, j+1), 1);
            }
            if(i+1 < N and S[i+1][j] == '.'){
                G.add_edge(d(i, j), d(i+1, j), 1);
            }
            if(i-1 >= 0 and S[i-1][j] == '.'){
                G.add_edge(d(i, j), d(i-1, j), 1);
            }
            if(j-1 >= 0 and S[i][j-1] == '.'){
                G.add_edge(d(i, j), d(i, j-1), 1);
            }
        } // end j
    } // end i
    cout << G.flow(s, t) << endl;
    auto e = G.edges();
    for (auto &&ex : e) {
        if(ex.from == s or ex.to == t) continue;
        if(ex.flow > 0){
            int vx, vy, ux, uy;
            tie(vx, vy) = rd(ex.from);
            tie(ux, uy) = rd(ex.to);
            if(vx == ux){
                if(vy > uy){
                    swap(vy, uy);
                }
                S[vx][vy] = '>';
                S[ux][uy] = '<';
            }
            else{
                if(vx > ux){
                    swap(vx, ux);
                }
                S[vx][vy] = 'v';
                S[ux][uy] = '^';
            }
        }
    } // end ex
    for (int i = 0; i < S.size(); ++i) {
        cout << S[i] << '\n';
    } // end i

}

int main(int argc, char *argv[]) {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(16) << scientific;
#ifdef XELMH
    string test_cases = "test_d.txt";
    cerr << test_cases << " -->" << endl;
    auto fs = fstream(test_cases, fstream::in);
    int loop = 0;
    while(fs) {
        loop++;
        cout << '#' << loop << "#------\n";
        solver(fs, cout).run();
    }
    if(loop <= 1) {
        cout << "===" << endl;
        while(cin) solver(cin, cout).run();
    }
#else
    solver(cin, cout).run();
#endif
    return 0;
}


Measured memory_bytes: 5556