#![allow(unused_imports)]
#![allow(non_snake_case, unused)]

use std::cmp::*;
use std::collections::*;
use std::ops::*;

// https://atcoder.jp/contests/hokudai-hitachi2019-1/submissions/10518254 より

macro_rules! eprint {
    ($($t:tt)*) => {{
        use ::std::io::Write;
        let _ = write!(::std::io::stderr(), $($t)*);
    }};
}
macro_rules! eprintln {
    () => { eprintln!(""); };
    ($($t:tt)*) => {{
        use ::std::io::Write;
        let _ = writeln!(::std::io::stderr(), $($t)*);
    }};
}
macro_rules! dbg {
    ($v:expr) => {{
        let val = $v;
        eprintln!("[{}:{}] {} = {:?}", file!(), line!(), stringify!($v), val);
        val
    }}
}

macro_rules! mat {
    ($($e:expr),*) => { Vec::from(vec![$($e),*]) };
    ($($e:expr,)*) => { Vec::from(vec![$($e),*]) };
    ($e:expr; $d:expr) => { Vec::from(vec![$e; $d]) };
    ($e:expr; $d:expr $(; $ds:expr)+) => { Vec::from(vec![mat![$e $(; $ds)*]; $d]) };
}

macro_rules! ok {
    ($a:ident$([$i:expr])*.$f:ident()$(@$t:ident)*) => {
        $a$([$i])*.$f($($t),*)
    };
    ($a:ident$([$i:expr])*.$f:ident($e:expr$(,$es:expr)*)$(@$t:ident)*) => { {
        let t = $e;
        ok!($a$([$i])*.$f($($es),*)$(@$t)*@t)
    } };
}

pub fn readln() -> String {
    let mut line = String::new();
    ::std::io::stdin().read_line(&mut line).unwrap_or_else(|e| panic!("{}", e));
    line
}

macro_rules! read {
    ($($t:tt),*; $n:expr) => {{
        let stdin = ::std::io::stdin();
        let ret = ::std::io::BufRead::lines(stdin.lock()).take($n).map(|line| {
            let line = line.unwrap();
            let mut it = line.split_whitespace();
            _read!(it; $($t),*)
        }).collect::<Vec<_>>();
        ret
    }};
    ($($t:tt),*) => {{
        let line = readln();
        let mut it = line.split_whitespace();
        _read!(it; $($t),*)
    }};
}

macro_rules! _read {
    ($it:ident; [char]) => {
        _read!($it; String).chars().collect::<Vec<_>>()
    };
    ($it:ident; [u8]) => {
        Vec::from(_read!($it; String).into_bytes())
    };
    ($it:ident; usize1) => {
        $it.next().unwrap_or_else(|| panic!("input mismatch")).parse::<usize>().unwrap_or_else(|e| panic!("{}", e)) - 1
    };
    ($it:ident; [usize1]) => {
        $it.map(|s| s.parse::<usize>().unwrap_or_else(|e| panic!("{}", e)) - 1).collect::<Vec<_>>()
    };
    ($it:ident; [$t:ty]) => {
        $it.map(|s| s.parse::<$t>().unwrap_or_else(|e| panic!("{}", e))).collect::<Vec<_>>()
    };
    ($it:ident; $t:ty) => {
        $it.next().unwrap_or_else(|| panic!("input mismatch")).parse::<$t>().unwrap_or_else(|e| panic!("{}", e))
    };
    ($it:ident; $($t:tt),+) => {
        ($(_read!($it; $t)),*)
    };
}


pub fn main() {
    let _ = ::std::thread::Builder::new().name("run".to_string()).stack_size(32 * 1024 * 1024).spawn(run).unwrap().join();
}

const MOD: usize = 998244353;
// const MOD: usize = 1_000_000_007;
const INF: i64 = std::i64::MAX/2;

#[derive(Copy,Clone)]
struct Edge {
	to: usize,
	cap: i64,
	rev: usize,
}

struct Dinic {
	edge: Vec<Vec<Edge>>,
	level: Vec<i64>,
	iter: Vec<usize>,
	n: usize,
}

impl Dinic {
	pub fn new(n: usize) -> Self {
		Dinic {
			edge: vec![vec![];n],
			level: vec![-1;n],
			iter: vec![0;n],
			n: n,
		}
	}

	pub fn add_edge(&mut self, s: usize, t: usize, c: i64) {
		let mut tmp = self.edge[t].len();
		self.edge[s].push(Edge{to: t, cap: c, rev: tmp});
		let mut tmp = self.edge[s].len();
		self.edge[t].push(Edge{to: s, cap: 0, rev: tmp-1});
	}

	pub fn add_multi_edge(&mut self, s: usize, t: usize, c: i64) {
		let mut tmp = self.edge[t].len();
		self.edge[s].push(Edge{to: t, cap: c, rev: tmp});
		let mut tmp = self.edge[s].len();
		self.edge[t].push(Edge{to: s, cap: c, rev: tmp-1});
	}

	pub fn bfs(&mut self, s: usize) {
		self.level = vec![-1;self.n];
		self.level[s] = 0;
		let mut q = VecDeque::new();
		q.push_back(s);
		while let Some(cur) = q.pop_front() {
			for &e in &self.edge[cur] {
				if e.cap > 0 && self.level[e.to] < 0 {
					self.level[e.to] = self.level[cur] + 1;
					q.push_back(e.to);
				}
			}
		}
	} 

	pub fn dfs(&mut self, v: usize, t: usize, val: i64) -> i64{
		if v==t {
			return val;
		}
		for i in self.iter[v]..self.edge[v].len() {
			let e = self.edge[v][i];
			if e.cap > 0 && self.level[v] < self.level[e.to] {
				let d = self.dfs(e.to,t,min(val,e.cap));
				if d > 0 {
					self.edge[v][i].cap -= d;
					self.edge[e.to][e.rev].cap += d;
					return d;
				}
			}
			self.iter[v] += 1;
		}
		return 0;
	}

	pub fn calc(&mut self, s: usize, t: usize) -> i64{
		let mut flow = 0;
		loop {
			self.bfs(s);
			if self.level[t] < 0 {
				return flow;
			}
			self.iter = vec![0;self.n];
			let mut f = 0;
			loop {
				let ret = self.dfs(s,t,INF);
				if ret == 0 {
					break;
				}
				f += ret;
			}
			flow += f;
		}
	}

}
fn solve() {
    let (n,m) = read!(usize,usize);
    let board = read!([char];n);
    let mut dinic = Dinic::new(n*m+2);
    for i in 0..n {
        for j in 0..m {
            if board[i][j]=='#' {
                continue;
            }
            if (i+j)%2==1 {
                dinic.add_edge(i*m+j+1,n*m+1,1);
                continue;
            }
            dinic.add_edge(0,i*m+j+1,1);
            let dir = [(1,0),(0,1),(-1,0),(0,-1)];
            for (ndir,&(dx,dy)) in dir.iter().enumerate() {
                let nx = i.wrapping_add(dx as usize);
                let ny = j.wrapping_add(dy as usize);
                if nx>=n || ny>=m {
                    continue;
                }
                if board[nx][ny]=='#' {
                    continue;
                }
                dinic.add_edge(i*m+j+1,nx*m+ny+1,1);
            }
        }
    }
    let val = dinic.calc(0,n*m+1);
    let mut ans = board.clone();
    for &e in &dinic.edge[0] {
        if e.cap==1 {
            continue;
        }
        for &c in &dinic.edge[e.to] {
            if c.cap==1 {
                continue;
            }
            let (px,py) = ((e.to-1)/m,(e.to-1)%m);
            let (nx,ny) = ((c.to-1)/m,(c.to-1)%m);
            if px==nx {
                ans[px][min(py,ny)] = '>';
                ans[px][max(py,ny)] = '<';
            }
            else {
                ans[min(px,nx)][py] = 'v';
                ans[max(px,nx)][py] = '^';
            }
        }
    }
    println!("{}",val);
    for i in 0..n {
        for j in 0..m {
            print!("{}",ans[i][j]);
        }
        println!();
    }
}

fn run() {
    solve();
}


Measured memory_bytes: 4744