#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

#ifdef _MSC_VER
#include <intrin.h>

#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
#endif

#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include<atcoder/all>

using namespace std;

using namespace atcoder;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (int i = m; i < n; ++i)
#define FORR(i, m, n) for (int i = m - 1; i >= n; --i)
#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define REVERSE(v, n) reverse(v, v + n);
#define VREVERSE(v) reverse(v.begin(), v.end())
#define ll long long
#define print(x) cout << (x) << endl
#define pe(x) cout << (x) << " "
#define DEBUG(x) cout << #x << ": " << x << endl
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
#define int long long
//#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i, v.size()) cout << v[i] << " \n"[i==(int)v.size()-1]
template <typename T1, typename T2> inline void chmin(T1& a, T2 b) { if (a > b) a = b; }
template <typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 1e9 + 7;
constexpr int MAX = 500050;
const double pi = acos(-1);
constexpr double EPS = 1e-8;
constexpr ll LINF = 1e18 + 1;
constexpr int INF = 1e9 + 1;
void Yes(bool cond) { cout << (cond ? "Yes" : "No") << '\n'; }
void YES(bool cond) { cout << (cond ? "YES" : "NO") << '\n'; }

int N, M;
int co(int i, int j) {
	return i * M + j;
}
pii oc(int n) {
	return{ n / M,n%M };
}

char A[101][101];

char B[101][101];
void solve() {
	cin >> N >> M;
	mf_graph<ll>G(N*M + 2);
	int K = N * M;
	int s = K, t = K + 1;
	REP(i, N)REP(j, M) {
		cin >> A[i][j];
		B[i][j] = A[i][j];
	}
	REP(i, N) {
		REP(j, M) {
			if (A[i][j] == '.') {
				if ((i + j)%2==0) {
					G.add_edge(s, co(i, j), 1);
					if (j + 1 < M&&A[i][j + 1] == '.')G.add_edge(co(i, j), co(i, j + 1), 1);
					if (i + 1 < N&&A[i + 1][j] == '.')G.add_edge(co(i, j), co(i + 1, j), 1);
					if (j - 1 >= 0 && A[i][j - 1] == '.')G.add_edge(co(i, j), co(i, j - 1), 1);
					if (i - 1 >= 0 && A[i - 1][j] == '.')G.add_edge(co(i, j), co(i - 1, j), 1);
				}
				else G.add_edge(co(i, j), t, 1);

			}
		}
	}
	ll ans = G.flow(s, t);
	vector<mf_graph<ll>::edge>es = G.edges();
	for (auto e : es) {
		if (e.from < K&&e.flow>0&&e.to<K) {
			int x = oc(e.from).first, y = oc(e.from).second;
			int nx = oc(e.to).first, ny = oc(e.to).second;
			//cerr << x << " " << y << " " << nx << " " << ny << endl;
			if (x > nx)swap(x, nx);
			if (y > ny)swap(y, ny);
			if (nx == x + 1) {
				B[x][y] = 'v';
				B[nx][ny] = '^';
			}
			else if(ny==y+1) {
				B[x][y] = '>';
				B[nx][ny] = '<';
			}
		}
	}
	print(ans);
	REP(i, N) {
		REP(j, M) {
			cout << B[i][j];
		}cout << '\n';
	}
}



signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	//int q;
	//cin >> q;
	//while (q--)
	solve();

}



Measured memory_bytes: 6336