#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#include<random>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (int)(Y);++(X))
#define reps(X,S,Y) for (int (X) = (int)(S);(X) < (int)(Y);++(X))
#define rrep(X,Y) for (int (X) = (int)(Y)-1;(X) >=0;--(X))
#define rreps(X,S,Y) for (int (X) = (int)(Y)-1;(X) >= (int)(S);--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl
#define NL <<"\n"
#define cauto const auto

using namespace std;
using ll=long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
template<class T> using vv=vector<vector<T>>;
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
//#undef NUIP
#ifdef NUIP
#include "benri.h"
#else
#define out(args...)
#endif
#ifdef __cpp_init_captures
template<typename T>vector<T> table(int n, T v){ return vector<T>(n, v);}
template <class... Args> auto table(int n, Args... args){auto val = table(args...); return vector<decltype(val)>(n, move(val));}
#endif
template<class A,class B> pair<A,B> operator+(const pair<A,B> &p,const pair<A,B> &q){ return {p.X+q.X,p.Y+q.Y};}
template<class A,class B,class C,class D> pair<A,B>& operator+=(pair<A,B> &p,const pair<C,D> &q){ p.X+=q.X; p.Y+=q.Y; return p;}
template<class A,class B> pair<A,B> operator-(const pair<A,B> &p,const pair<A,B> &q){ return {p.X-q.X,p.Y-q.Y};}
template<class A,class B,class C,class D> pair<A,B>& operator-=(pair<A,B> &p,const pair<C,D> &q){ p.X-=q.X; p.Y-=q.Y; return p;}
template<class A,class B> istream& operator>>(istream &is, pair<A,B> &p){ is>>p.X>>p.Y; return is;}
template<class T=ll> T read(){ T re; cin>>re; return move(re);}
template<class T=ll> T read(const T &dec){ T re; cin>>re; return re-dec;}
template<class T=ll> vector<T> readV(const int sz){ vector<T> re(sz); for(auto &x:re) x=read<T>(); return move(re);}
template<class T=ll> vector<T> readV(const int sz, const T &dec){ vector<T> re(sz); for(auto &x:re) x=read<T>(dec); return move(re);}
vv<int> readG(const int &n,const int &m){ vv<int> g(n); rep(_,m){ cauto a=read<int>(1),b=read<int>(1); g[a].pb(b); g[b].pb(a);} return move(g);}
vv<int> readG(const int &n){ return readG(n,n-1);}
const ll MOD=1e9+7; //998244353

#include <atcoder/all>
using namespace atcoder;

int main(){
  ios_base::sync_with_stdio(false); cin.tie(0);
  cout<<fixed<<setprecision(0);
	cauto n=read();
	cauto m=read();
	cauto mp=readV<string>(n);
	mf_graph<int> g(n*m*2+2);
	cauto S=n*m*2;
	cauto T=n*m*2+1;
	cauto fun=[&](int i,int j){ return i*m+j;};
	cauto add=
		[&](int a,int b,bool f){
			out(a,b,1);
			if(f){
				g.add_edge(b,n*m+a,1);	
			}else{
				g.add_edge(a,n*m+b,1);
			}
	};
	rep(i,n)rep(j,m)if(mp[i][j]=='.'){
		cauto t=i%2==j%2;
		if(t) g.add_edge(S,fun(i,j),1);
		else g.add_edge(n*m+fun(i,j),T,1);
		if(i && mp[i-1][j]=='.') add(fun(i-1,j),fun(i,j),t);
		if(j && mp[i][j-1]=='.') add(fun(i,j-1),fun(i,j),t);
	}
	cout<<g.flow(S,T) NL;
	cauto es=g.edges();
	auto re=mp;
	for(cauto &e:es)if(e.cap==e.flow && e.to!=T && e.from!=S){
			cauto x=e.from%m;
			cauto y=e.from/m%n;
			cauto X=e.to%m;
			cauto Y=e.to/m%n;
			out(x,y,X,Y,e.from,e.to,1);
			if(x==X){
				re[min(y,Y)][x]='v';
				re[max(y,Y)][x]='^';
			}else{
				re[y][min(x,X)]='>';
				re[y][max(x,X)]='<';
			}
		}
	for(auto s:re) cout<<s NL; 
  return 0;
}


Measured memory_bytes: 5868