static void Main()
{
var(n, m) = Read2();
var s = Array.ConvertAll(new bool[n], _ => Console.ReadLine().ToCharArray());
var vs0 = new List <int>();
var vs1 = new List <int>();
var vs1Inv = Array.ConvertAll(new bool[n * m], _ => - 1);
// checker board
for (int i = 0; i < n; i++)
{
for (int j = 0; j < m; j++)
{
if (s[i][j] == '#')
{
continue;
}
var v = m * i + j;
if ((i + j) % 2 == 0)
{
vs0.Add(v);
}
else
{
vs1Inv[v] = vs1.Count;
vs1.Add(v);
}
}
}
var bm = new BipartiteMatching(vs0.Count, vs1.Count);
for (int i = 0; i < vs0.Count; i++)
{
var v = vs0[i];
if (v - m >= 0 && vs1Inv[v - m] != -1)
{
bm.AddEdge(i, vs1Inv[v - m]);
}
if (v + m < n * m && vs1Inv[v + m] != -1)
{
bm.AddEdge(i, vs1Inv[v + m]);
}
if (v % m != 0 && vs1Inv[v - 1] != -1)
{
bm.AddEdge(i, vs1Inv[v - 1]);
}
if (v % m != m - 1 && vs1Inv[v + 1] != -1)
{
bm.AddEdge(i, vs1Inv[v + 1]);
}
}
var res = bm.Dinic();
foreach (var e in res)
{
var v0 = vs0[e[0]];
var v1 = vs1[e[1]];
var(i0, j0) = (v0 / m, v0 % m);
var(i1, j1) = (v1 / m, v1 % m);
if (i0 == i1)
{
s[i0][Math.Min(j0, j1)] = '>';
s[i0][Math.Max(j0, j1)] = '<';
}
else
{
s[Math.Min(i0, i1)][j0] = 'v';
s[Math.Max(i0, i1)][j0] = '^';
}
}
Console.WriteLine(res.Length);
foreach (var r in s)
{
Console.WriteLine(new string(r));
}
}
