// https://atcoder.jp/contests/practice2/tasks/practice2_d
//
#![allow(unused_imports)]
use std::io::*;
use std::io::Write;
use std::fmt::*;
use std::str::*;
use std::cmp::*;
use std::collections::*;

// Input macros.
// Original by tanakh: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[allow(unused_macros)]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

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

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

#[allow(unused_macros)]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };

    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };

    ($iter:expr, [ next / $t:tt ]) => {
        {
            let len = read_value!($iter, usize);
            (0..len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
        }
    };

    ($iter:expr, switch) => {
        {
            let ty = read_value!($iter, i32);
            if ty == 1 {
                vec![ty, read_value!($iter, i32), read_value!($iter, i32)]
            } else if ty == 2 {
                vec![ty, read_value!($iter, i32)]
            } else {
                vec![ty, read_value!($iter, i32)]
            }
        }
    };

    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };

    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };

    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

#[allow(unused_macros)]
macro_rules! read_line {
    ($t:tt) => {
        {
            let mut s = String::new();
            std::io::stdin().read_line(&mut s).unwrap();
            s.trim_right().parse::<$t>().unwrap()
        }
    }
}

#[allow(unused_macros)]
macro_rules! dvec {
    ($t:expr ; $len:expr) => {
        vec![$t; $len]
    };

    ($t:expr ; $len:expr, $($rest:expr),*) => {
        vec![dvec!($t; $($rest),*); $len]
    };
}

#[allow(unused_macros)]
macro_rules! ifv {
    ($t:expr, $a:expr, $b: expr) => {
        if $t { $a } else { $b }
    }
}

#[allow(unused_macros)]
macro_rules! fill {
    ($t:expr, $v:expr) => {
        for i in 0..$t.len() {
            $t[i] = $v;
        }
    };
}

#[allow(unused_macros)]
macro_rules! join {
    ($t:expr, $glue:expr) => {
        $t.into_iter().map(|w| w.to_string()).collect::<Vec<_>>().join($glue)
    };
}

#[allow(unused_macros)]
macro_rules! debug {
    ($($a:expr),*) => {
        println!(concat!($(stringify!($a), " = {:?}, "),*), $($a),*);
    }
}

// ===

const MAX_FLOW: i32 = 100000000;

#[derive(Clone, Copy)]
struct Edge {
    from: usize,
    to: usize,
    cap: i32,
    maxcap: i32,
    label: usize,
}

impl Edge {
    fn goto(&self, from: usize) -> usize {
        self.from + self.to - from
    }

    fn cap(&self, from: usize) -> i32 {
        if self.from == from {
            self.cap
        } else {
            self.maxcap - self.cap
        }
    }
}

struct FlowGraph {
    n: usize,
    graph: Vec<Vec<usize>>,
    edges: Vec<Edge>,
    level: Vec<i32>,
    itr: Vec<usize>
}

impl FlowGraph {
    fn new(n: usize) -> Self {
        let graph = vec![vec![]; n];
        let level = vec![0; n];
        let itr = vec![0; n];
        FlowGraph { n: n, graph: graph, edges: vec![], level: level, itr: itr }
    }

    fn add_edge(&mut self, from: usize, to: usize, cap: i32, label: usize) {
        let e = Edge { from: from, to: to, cap: cap, maxcap: cap, label: label };
        let l = self.edges.len();
        self.graph[from].push(l);
        self.graph[to].push(l);
        self.edges.push(e);
    }

    fn dfs(&mut self, now: usize, to: usize, flow: i32) -> i32 {
        if now == to {
            return flow;
        }
        for i in self.itr[now]..self.graph[now].len() {
            self.itr[now] = i;
            let eidx = self.graph[now][i];

            let e = self.edges[eidx];
            let next = e.goto(now);
            let ecap = e.cap(now);
            if ecap > 0 && self.level[now] < self.level[next] {
                let d = self.dfs(next, to, min(flow, ecap));
                if d >= 1 {
                    let e = &mut self.edges[eidx];
                    if e.from == now {
                        e.cap -= d;
                    } else {
                        e.cap += d;
                    }
                    return d;
                }
            }

        }
        return 0;
    }

    fn bfs(&mut self, from: usize) {
        for i in 0..self.n {
            self.level[i] = -1;
        }
        self.level[from] = 0;
        let mut q: VecDeque<usize> = VecDeque::new();
        q.push_back(from);
        while let Some(idx) = q.pop_front() {
            for &eidx in &self.graph[idx] {
                let e = &self.edges[eidx];
                let to = e.goto(idx);
                if e.cap(idx) >= 1 && self.level[to] == -1 {
                    self.level[to] = self.level[idx] + 1;
                    q.push_back(to);
                }
            }
        }
    }

    fn max_flow(&mut self, from: usize, to: usize) -> i32 {
        let mut flow = 0;
        loop {
            self.bfs(from);
            if self.level[to] < 0 {
                return flow;
            }
            for i in 0..self.n {
                self.itr[i] = 0;
            }
            loop {
                let f = self.dfs(from, to, MAX_FLOW);
                if f <= 0 {
                    break;
                }
                flow += f;
            }
        }
    }
}

fn detect_order(ay: usize, ax: usize, by: usize, bx: usize) -> ((usize,usize),(usize,usize),char,char) {
    // debug!(ay,ax,by,bx);
    assert!((ay == by) ^ (ax == bx));

    if ay == by {
        ((ay,min(ax,bx)), (ay,max(ax,bx)), '>', '<')
    } else {
        ((min(ay,by),ax), (max(ay,by),ax), 'v', '^')
    }
}

fn main() {
    input! {
        n: usize, m: usize,
        mut table: [chars; n]
    };


    let cell_id = |i: usize, j: usize| {
        i*m+j
    };

    let mut flow = FlowGraph::new(n*m+2);
    let source = n*m;
    let sink = source+1;
    for i in 0..n {
        for j in 0..m {
            if table[i][j] == '#' {
                continue;
            }

            if (i+j)&1 == 0 {
                flow.add_edge(source, cell_id(i,j), 1, 0);
            } else {
                flow.add_edge(cell_id(i,j), sink, 1, 0);
            }
        }
    }


    let dx = [1,0,1,2];
    let dy = [0,1,2,1];
    for i in 0..n {
        for j in 0..m {
            if table[i][j] == '#' {
                continue;
            }
            if (i+j)&1 == 0 {
                for d in 0..4 {
                    let ti = i+dy[d];
                    let tj = j+dx[d];
                    if ti == 0 || tj == 0 || ti >= n+1 || tj >= m+1 {
                        continue;
                    }
                    let ti = ti-1;
                    let tj = tj-1;
                    if table[ti][tj] == '#' {
                        continue;
                    }
                    flow.add_edge(cell_id(i,j), cell_id(ti,tj), 1, 1);
                }
            }
        }
    }

    let max_flow = flow.max_flow(source, sink);
    for i in 0..n {
        for j in 0..m {
            if table[i][j] == '#' || (i+j)&1==1 {
                continue;
            }
            for &eid in &flow.graph[cell_id(i,j)] {
                if flow.edges[eid].cap == 0 && flow.edges[eid].label == 1 {
                    let tid = flow.edges[eid].from+flow.edges[eid].to-cell_id(i,j);
                    let ti = tid/m;
                    let tj = tid%m;
                    let (f, t, a, b) = detect_order(i, j, ti, tj);
                    table[f.0][f.1] = a;
                    table[t.0][t.1] = b;
                }
            }
        }
    }

    println!("{}", max_flow);
    for c in table {
        println!("{}", join!(c, ""));
    }
}


Measured memory_bytes: 4348