///////////////////////////////////////////////////////////////////////////////

#include <bits/stdc++.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>

using namespace std;

///////////////////////////////////////////////////////////////////////////////

#define DEBUG 0

#define pb push_back
#define V vector
#define M unordered_map
#define S static

#define rep(i,n) for(ll i=0LL; i<n; ++i)
#define srep(i,s,n) for(ll i=s; i<n; ++i)
#define rrep(i,n) for(ll i=n-1LL; i>=0LL; --i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CIN(x) do { \
        assert(!cin.eof()); \
        cin >> x; \
        assert(!cin.fail()); \
} while(0);
#if DEBUG
#define debug_print(...) _debug_print(__VA_ARGS__)
#define debug_printf(...) printf(__VA_ARGS__)
#define debug_print_time _debug_print_time
#else // DEBUG
#define debug_print(...)
#define debug_printf(...)
#define debug_print_time
#endif // DEBUG

typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll, ll> t2;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;
typedef tuple<ll, ll, ll, ll, ll> t5;
template <typename T>
using priority_queue_incr = priority_queue<T, V<T>, greater<T> >;

///////////////////////////////////////////////////////////////////////////////

template <typename TT, typename T>
T get_m(M<TT, T> &m, TT k, T default_value)
{
    if (m.find(k) == m.end()) return m[k] = default_value;
    return m[k];
}

template <typename TT, typename T>
void incr_m(M<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

template <typename TT, typename T>
void incr_m(map<TT, T> &m, TT k)
{
    if (m.find(k) == m.end()) m[k] = 0;
    m[k]++;
}

void llin(ll &a)
{
    CIN(a);
}

void llinl1(V<ll> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a;
        CIN(a);
        v.push_back(a);
    }
}

void llinl2(V<t2> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b;
        CIN(a >> b);
        v.push_back(t2(a, b));
    }
}

void llinl3(V<t3> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c;
        CIN(a >> b >> c);
        v.push_back(t3(a, b, c));
    }
}

void llinl4(V<t4> &v, ll count)
{
    for (ll i = 0LL; i < count; ++i) {
        ll a, b, c, d;
        CIN(a >> b >> c >> d);
        v.push_back(t4(a, b, c, d));
    }
}

void llina(V<ll> &v, ll count)
{
    llinl1(v, count);
}

template <typename T>
void sort(V<T> &v)
{
    sort(v.begin(), v.end());
}

template <typename T>
void sort_reverse(V<T> &v)
{
    sort(v.begin(), v.end(), greater<T>());
}

template <typename T>
void _debug_print(T x)
{
    cout << x << endl;
}

void _debug_print(const t2 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    cout << "-- " << x1 << " -- " << x2 << endl;
}

void _debug_print(const t3 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    cout << "-- " << x1 << " -- " << x2 << " -- " << x3 << endl;
}

void _debug_print(const t4 &x)
{
    ll x1 = get<0>(x);
    ll x2 = get<1>(x);
    ll x3 = get<2>(x);
    ll x4 = get<3>(x);
    cout << "-- " << x1 << " -- " << x2
         << " -- " << x3 << " -- " << x4 << endl;
}

template <typename T>
void _debug_print(T xarray[], ll n)
{
    rep (i, n) _debug_print(xarray[i]);
}

template <typename T>
void _debug_print(const V<T> &xlist)
{
    for (auto x : xlist) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename T>
void _debug_print(const set<T> &xset)
{
    for (auto x : xset) {
        cout << "-- ";
        _debug_print(x);
    }
}

template <typename TT, typename T>
void _debug_print(const M<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

template <typename TT, typename T>
void _debug_print(const map<TT, T> &xlist)
{
    for (auto x : xlist) {
        TT k = x.first;
        T v = x.second;
        cout << "====" << endl;
        cout << "K=";
        _debug_print(k);
        cout << "V=";
        _debug_print(v);
    }
}

///////////////////////////////////////////////////////////////////////////////

void _main();
int main()
{
    cout << setprecision(12);
#if !DEBUG
    ios::sync_with_stdio(false);
    cin.tie(0);
#endif

    _main();
    return 0;
}

struct MaxFlow {
    V<ll> links[10010];
    ll capacities[10010][10010];
    ll idxs[10010];
    ll nodes;

    MaxFlow(ll nodes) {
        // i == 0       --> S
        // i == nodes+1 --> T
        rep (i, nodes+2LL) links[i].clear();
        memset(capacities, 0, sizeof(capacities));
        memset(idxs, 0, sizeof(idxs));
        this->nodes = nodes;
    }

    void add_link(ll a, ll b, ll capacity) {
        links[a].pb(b);
        links[b].pb(a);
        debug_printf("a=%lld b=%lld\n", a, b);
        capacities[a][b] = capacity;
        capacities[b][a] = 0LL;
    }

    bool find_path(deque<ll> &path, set<ll> &checked, ll v) {
        if (checked.find(v) != checked.end()) return false;

        checked.insert(v);
        path.push_back(v);
        if (v == nodes+1) return true;

        rep (xxx, links[v].size()) {
            ll nv = links[v][(idxs[v]++)%links[v].size()];
            if (capacities[v][nv] == 0) continue;
            if (find_path(path, checked, nv)) return true;
        }

        // checked.erase(v);
        path.pop_back();
        return false;
    }

    ll solve(void) {
        ll ret = 0LL;

        for ( ; ; ) {

            set<ll> checked;
            deque<ll> foundq;
            bool is_found = find_path(foundq, checked, 0);

            if (!is_found) break;

            V<ll> found;
            while (foundq.size()) {
                ll v = foundq.front(); foundq.pop_front();
                found.pb(v);
            }

            ll flowcount = 1e18;
            rep (i, (ll)found.size()-1LL) {
                ll src = found[i];
                ll dst = found[i+1];
                flowcount = min(flowcount, capacities[src][dst]);
            }
            rep (i, (ll)found.size()-1LL) {
                ll src = found[i];
                ll dst = found[i+1];
                capacities[src][dst] -= flowcount;
                capacities[dst][src] += flowcount;
            }
            ret += flowcount;

        }

        return ret;
    }
};






bool valid(const V<string> &grid, ll h, ll w, ll hh, ll ww)
{
    if (hh < 0) return false;
    if (hh >= h) return false;
    if (ww < 0) return false;
    if (ww >= w) return false;
    if (grid[hh][ww] == '#') return false;
    return true;
}

void _main()
{
    ll h; llin(h);
    ll w; llin(w);
    S V<string> grid;
    rep (i, h) {
        string tmp; CIN(tmp);
        grid.pb(tmp);
    }

    ll nodes = 10005;
    S MaxFlow flow(nodes);

    rep (hh, h) rep (ww, w) {
        if ((hh+ww) & 1LL) flow.add_link(hh*w + ww + 1, nodes+1, 1);
        else flow.add_link(0, hh*w + ww + 1, 1);
    }

    ll diff_h[4] = {-1, 0, 0, 1};
    ll diff_w[4] = {0, -1, 1, 0};
    V<t2> paths;

    rep (hh, h) rep (ww, w) {
        if ((hh+ww) & 1LL) continue;
        if (grid[hh][ww] == '#') continue;
        rep (i, 4) {
            ll hhh = hh + diff_h[i];
            ll www = ww + diff_w[i];
            if (valid(grid, h, w, hhh, www)) {
                flow.add_link(hh*w + ww + 1, hhh*w + www + 1, 1);
                paths.pb(t2(hh*w + ww + 1, hhh*w + www + 1));
            }
        }
    }

    ll anscnt = flow.solve();

    for (auto path : paths) {
        ll x1 = get<0>(path);
        ll x2 = get<1>(path);
        debug_printf("--------\n");
        if (flow.capacities[x1][x2]) continue;
        debug_printf("---- f=%lld\n", flow.capacities[x1][x2]);
        x1--;
        x2--;
        ll h1 = x1 / w;
        ll w1 = x1 % w;
        ll h2 = x2 / w;
        ll w2 = x2 % w;
        debug_printf("h1=%lld h2=%lld w1=%lld w2=%lld\n", h1, h2, w1, w2);
        if (h1 == h2) {
            ll wmin = min(w1, w2);
            ll wmax = max(w1, w2);
            grid[h1][wmin] = '>';
            grid[h1][wmax] = '<';
        }
        else {
            ll hmin = min(h1, h2);
            ll hmax = max(h1, h2);
            grid[hmin][w1] = 'v';
            grid[hmax][w1] = '^';
        }
    }

    debug_printf("----- ans\n");

    cout << anscnt << endl;
    rep (hh, h) {
        rep (ww, w) {
            cout << grid[hh][ww];
        }
        cout << endl;
    }
}

///////////////////////////////////////////////////////////////////////////////


Measured memory_bytes: 788524