#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::{Write, BufWriter};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};
    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, [graph1; $len:expr]) => {{
        let mut g = vec![vec![]; $len];
        let ab = read_value!($next, [(usize1, usize1)]);
        for (a, b) in ab {
            g[a].push(b);
            g[b].push(a);
        }
        g
    }};
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };
    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };
    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };
    ($next:expr, usize1) => (read_value!($next, usize) - 1);
    ($next:expr, [ $t:tt ]) => {{
        let len = read_value!($next, usize);
        read_value!($next, [$t; len])
    }};
    ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));
}

/**
 * Dinic's algorithm for maximum flow problem.
 * Verified by: yukicoder No.177 (http://yukicoder.me/submissions/148371)
 * Min-cut (the second element of max_flow's returned values) is not verified.
 */

#[derive(Clone)]
struct Edge<T> {
    to: usize,
    cap: T,
    rev: usize, // rev is the position of the reverse edge in graph[to]
}

struct Dinic<T> {
    graph: Vec<Vec<Edge<T>>>,
    iter: Vec<usize>,
    zero: T,
}

impl<T> Dinic<T>
    where T: Clone,
          T: Copy,
          T: Ord,
          T: std::ops::AddAssign,
          T: std::ops::SubAssign,
{
    fn bfs(&self, s: usize, level: &mut [Option<usize>]) {
        let n = level.len();
        for i in 0 .. n {
            level[i] = None;
        }
        let mut que = std::collections::VecDeque::new();
        level[s] = Some(0);
        que.push_back(s);
        while let Some(v) = que.pop_front() {
            for e in self.graph[v].iter() {
	        if e.cap > self.zero && level[e.to] == None {
	            level[e.to] = Some(level[v].unwrap() + 1);
	            que.push_back(e.to);
                }
            }
	}
    }
    /* search augment path by dfs.
     * if f == None, f is treated as infinity.
     */
    fn dfs(&mut self, v: usize, t: usize, f: Option<T>, level: &mut [Option<usize>]) -> T {
        if v == t {
            return f.unwrap();
        }
        while self.iter[v] < self.graph[v].len() {
            let i = self.iter[v];
            let e = self.graph[v][i].clone();
            if e.cap > self.zero && level[v] < level[e.to] {
                let newf = std::cmp::min(f.unwrap_or(e.cap), e.cap);
                let d = self.dfs(e.to, t, Some(newf), level);
                if d > self.zero {
                    self.graph[v][i].cap -= d;
                    self.graph[e.to][e.rev].cap += d;
                    return d;
                }
            }
            self.iter[v] += 1;
        }
        self.zero
    }
    pub fn new(n: usize, zero: T) -> Self {
        Dinic {
            graph: vec![Vec::new(); n],
            iter: vec![0; n],
            zero: zero,
        }
    }
    pub fn add_edge(&mut self, from: usize, to: usize, cap: T) {
        let added_from = Edge { to: to, cap: cap,
                            rev: self.graph[to].len() };
        let added_to = Edge { to: from, cap: self.zero,
                            rev: self.graph[from].len() };
        self.graph[from].push(added_from);
        self.graph[to].push(added_to);
    }
    pub fn max_flow(&mut self, s: usize, t: usize) -> (T, Vec<usize>) {
        let mut flow = self.zero;
        let n = self.graph.len();
        let mut level = vec![None; n];
        loop {
            self.bfs(s, &mut level);
            if level[t] == None {
                let ret = (0 .. n).filter(|&i| level[i] == None)
                    .collect();
                return (flow, ret);
            }
            self.iter.clear();
            self.iter.resize(n, 0);
            loop {
                let f = self.dfs(s, t, None, &mut level);
                if f <= self.zero { break; }
                flow += f;
            }
        }
    }
}

fn set(s: &mut [Vec<char>], v: usize, c: char) {
    let a = v / s[0].len();
    let b = v % s[0].len();
    s[a][b] = c;
}

fn solve() {
    let out = std::io::stdout();
    let mut out = BufWriter::new(out.lock());
    macro_rules! puts {
        ($($format:tt)*) => (let _ = write!(out,$($format)*););
    }
    input! {
        n: usize, m: usize,
        s: [chars; n],
    }
    let mut din = Dinic::new(n * m + 2, 0);
    
    for i in 0..n {
        for j in 0..m {
            if s[i][j] == '#' { continue; }
            if i + 1 < n {
                if s[i + 1][j] != '#' {
                    let a = i * m + j;
                    let b = (i + 1) * m + j;
                    if (i + j) % 2 == 0 {
                        din.add_edge(a, b, 1);
                    } else {
                        din.add_edge(b, a, 1);
                    }
                }
            }
            if j + 1 < m {
                if s[i][j + 1] != '#' {
                    let a = i * m + j;
                    let b = i * m + j + 1;
                    if (i + j) % 2 == 0 {
                        din.add_edge(a, b, 1);
                    } else {
                        din.add_edge(b, a, 1);
                    }
                }
            }
        }
    }
    for i in 0..n {
        for j in 0..m {
            if s[i][j] == '#' {
                continue;
            }
            if (i + j) % 2 == 0 {
                din.add_edge(n * m, i * m + j, 1);
            } else {
                din.add_edge(i * m + j, n * m + 1, 1);
            }
        }
    }
    let (ans, _) = din.max_flow(n * m, n * m + 1);
    let mut s = s;
    for i in 0..n * m {
        if (i / m + i % m) % 2 == 1 {
            continue;
        }
        for &Edge { to: v, cap, .. } in &din.graph[i] {
            if cap == 0 && v < n * m {
                let (x, y) = if v < i { (v, i) } else { (i, v) };
                if y - x == 1 && x % m < m - 1 {
                    set(&mut s, x, '>');
                    set(&mut s, y, '<');
                } else {
                    set(&mut s, x, 'v');
                    set(&mut s, y, '^');
                }
            }
        }
    }
    puts!("{}\n", ans);
    for i in 0..n {
        for j in 0..m {
            puts!("{}", s[i][j]);
        }
        puts!("\n");
    }
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}


Measured memory_bytes: 3940