from collections import deque
class MaxFlow:
inf = 10**18
class E:
def __init__(self,to,cap):
self.to = to
self.cap = cap
self.rev = None
def __init__(self,n):
self.n = n
self.graph = [[] for _ in range(n)]
def add_edge(self, fr, to, cap):
graph = self.graph
edge = self.E(to,cap)
edge2 = self.E(fr,0)
edge.rev = edge2
edge2.rev = edge
graph[fr].append(edge)
graph[to].append(edge2)
def bfs(self, s, t):
level = self.level = [self.n]*self.n
q = deque([s])
level[s] = 0
while q:
now = q.popleft()
lw = level[now]+1
for e in self.graph[now]:
if e.cap and level[e.to]> lw:
level[e.to] = lw
if e.to == t:
return True
q.append(e.to)
return False
def dfs(self, s, t, up):
graph = self.graph
it = self.it
level = self.level
st = deque([t])
while st:
v = st[-1]
if v == s:
st.pop()
flow = up
for w in st:
e = graph[w][it[w]].rev
flow = min(flow, e.cap)
for w in st:
e = graph[w][it[w]]
e.cap += flow
e.rev.cap -= flow
return flow
lv = level[v]-1
while it[v] < len(graph[v]):
e = graph[v][it[v]]
re = e.rev
if re.cap == 0 or lv != level[e.to]:
it[v] += 1
continue
st.append(e.to)
break
if it[v] == len(graph[v]):
st.pop()
level[v] = self.n
return 0
def flow(self,s,t,flow_limit=inf):
flow = 0
while flow < flow_limit and self.bfs(s,t):
self.it = [0]*self.n
while flow < flow_limit:
f = self.dfs(s,t,flow_limit-flow)
if f == 0:
break
flow += f
return flow
def min_cut(self,s):
visited = [False]*self.n
q = deque([s])
while q:
v = q.pop()
visited[v] = True
for e in self.graph[v]:
if e.cap and not visited[e.to]:
q.append(e.to)
return visited
n,m = map(int,input().split())
S = [list(input()) for i in range(n)]
s = n*m
t = s+1
flow = MaxFlow(t+1)
for i in range(n):
for j in range(m):
if S[i][j] == "#":
continue
if (i+j) % 2 == 0:
flow.add_edge(s,i*m+j,1)
else:
flow.add_edge(i*m+j,t,1)
for i in range(n):
for j in range(m):
if S[i][j] != ".":
continue
if j+1 < m and S[i][j+1] == ".":
u,v = m*i+j,m*i+j+1
if (i+j) % 2 == 1:
u,v = v,u
flow.add_edge(u, v, 1)
if i+1 < n and S[i+1][j] == ".":
u,v = m*i+j, m*(i+1)+j
if (i+j) % 2 == 1:
u,v = v,u
flow.add_edge(u,v,1)
print(flow.flow(s,t))
for u in range(s):
for e in flow.graph[u]:
v = e.to
ui, uj = divmod(u, m)
vi, vj = divmod(v, m)
if (ui+uj) % 2 == 0 and e.cap == 0 and v != s and v != t:
if ui+1 == vi:
S[ui][uj] = "v"
S[vi][vj] = "^"
elif ui == vi+1:
S[ui][uj] = "^"
S[vi][vj] = "v"
elif uj+1 == vj:
S[ui][uj] = ">"
S[vi][vj] = "<"
elif uj == vj+1:
S[ui][uj] = "<"
S[vi][vj] = ">"
for i in S:
print(*i,sep="")