#include <iostream>
#include <string>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <unordered_map>
#include <map>
#include <set>
#include <algorithm>
#include <queue>
#include <stack>
#include <functional>
#include <bitset>
#include <assert.h>
#include <unordered_map>
#include <fstream>
#include <ctime>
#include <complex>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef pair<ll,ll> P;
typedef pair<int,int> pii;
typedef vector<P> vpl;
typedef tuple<ll,ll,ll> tapu;
#define rep(i,n) for(int i=0; i<(n); i++)
#define REP(i,a,b) for(int i=(a); i<(b); i++)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const int inf = 1<<30;
const ll linf = 1LL<<62;
const int MAX = 510000;
ll dy[8] = {1,-1,0,0,1,-1,1,-1};
ll dx[8] = {0,0,1,-1,1,-1,-1,1};
const double pi = acos(-1);
const double eps = 1e-7;
template<typename T1,typename T2> inline bool chmin(T1 &a,T2 b){
	if(a>b){
		a = b; return true;
	}
	else return false;
}
template<typename T1,typename T2> inline bool chmax(T1 &a,T2 b){
	if(a<b){
		a = b; return true;
	}
	else return false;
}
template<typename T> inline void print(T &a){
    for(auto itr = a.begin(); itr != a.end(); itr++){
		cout << *itr << " ";
	}
    cout << "\n";
}
template<typename T1,typename T2> inline void print2(T1 a, T2 b){
	cout << "debug: " << a << " " << b << "\n";
}
template<typename T1,typename T2,typename T3> inline void print3(T1 a, T2 b, T3 c){
	cout << "debug: " << a << " " << b << " " << c << "\n";
}
void mark() {cout << "#" << "\n";}
ll pcount(ll x) {return __builtin_popcountll(x);}
const int mod = 1e9 + 7;
//const int mod = 998244353;

bool in(ll y, ll x, ll h, ll w){
    return 0 <= y && y < h && 0 <= x && x < w;
}

int main(){
	int n,m; cin >> n >> m;
    vs s(n); rep(i,n) cin >> s[i];
    mf_graph<int> flow(n*m+2);
    int S = n*m, T = n*m+1;
    rep(i,n){
        rep(j,m){
            if(s[i][j] == '#') continue;
            if((i+j) & 1 ^ 1){
                flow.add_edge(S,i*m+j,1);
                rep(k,4){
                    int ny = i + dy[k];
                    int nx = j + dx[k];
                    if(in(ny,nx,n,m) && s[ny][nx] == '.'){
                        flow.add_edge(i*m+j,ny*m+nx,1);
                    }
                }
            }else{
                flow.add_edge(i*m+j,T,1);
            }
        }
    }
    vs t = s;
    cout << flow.flow(S,T) << "\n";
    auto edges = flow.edges();
    for(auto e : edges){
        if(e.from == S || e.to == T || e.flow == 0) continue;
        int sy = e.from / m;
        int sx = e.from % m;
        int gy = e.to / m;
        int gx = e.to % m;
        if(sy == gy){
            if(sx == gx - 1){
                t[sy][sx] = '>';
                t[gy][gx] = '<'; 
            }else{
                t[gy][gx] = '>';
                t[sy][sx] = '<';
            }
        }else{
            if(sy == gy-1){
                t[sy][sx] = 'v';
                t[gy][gx] = '^';
            }else{
                t[gy][gx] = 'v';
                t[sy][sx] = '^';
            }
        }
    }
    rep(i,n) cout << t[i] << "\n";
}

Measured memory_bytes: 5500