mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    from collections import deque

    class Dinic:
        def __init__(self, N):
            self.N = N
            self.adj = [[] for _ in range(N + 1)]
            self.lv = None
            self.progress = None
            self.inf = 1 << 60

        def add_edge(self, fr, to, cap):
            # [to, cap, rev]
            forward = [to, cap, None]
            backward = forward[2] = [fr, 0, forward]
            self.adj[fr].append(forward)
            self.adj[to].append(backward)

        def bfs(self, s, t):
            que = deque([s])
            lv = [-1] * (self.N + 1)
            lv[s] = 0
            while que:
                v = que.popleft()
                lvv = lv[v]
                for u, cap, _ in self.adj[v]:
                    if cap and lv[u] == -1:
                        que.append(u)
                        lv[u] = lvv + 1
                        if u == t:
                            break
            self.lv = lv

        def dfs(self, s, t, flow):
            st = deque([s])
            st_f = deque([flow])
            while st:
                v = st[-1]
                f = st_f[-1]
                if v == t:
                    for i in range(len(st) - 1, 0, -1):
                        p = st[i - 1]
                        edge = self.adj[p][self.progress[p] - 1]
                        edge[1] -= f
                        edge[2][1] += f
                        v = p
                    return f
                if self.progress[v] == len(self.adj[v]):
                    st.pop()
                    st_f.pop()
                    continue
                else:
                    adj_v = self.adj[v]
                    for i in range(self.progress[v], len(adj_v)):
                        i = self.progress[v]
                        self.progress[v] = i + 1
                        u, cap, rev = adj_v[i]
                        if not cap or self.lv[u] != self.lv[v] + 1:
                            continue
                        else:
                            st.append(u)
                            st_f.append(min(st_f[-1], cap))
                            break

        def max_flow(self, s, t):
            flow = 0
            while True:
                self.bfs(s, t)
                if self.lv[t] < 0:
                    return flow
                self.progress = [0] * (self.N + 1)
                flow_new = self.dfs(s, t, self.inf)
                while flow_new:
                    flow += flow_new
                    flow_new = self.dfs(s, t, self.inf)

    H, W = map(int, input().split())
    grid = [[""] * W for _ in range(H)]
    for h in range(H):
        S = input().rstrip('\n')
        for w in range(W):
            grid[h][w] = S[w]

    D = Dinic(H * W + 2)
    s = H * W + 1
    t = H * W + 2
    dhw = [(0, 1), (0, -1), (1, 0), (-1, 0)]
    for h in range(H):
        for w in range(W):
            if (h+w)%2 == 0:
                D.add_edge(s, h*W + w + 1, 1)
            else:
                D.add_edge(h*W + w + 1, t, 1)
            if grid[h][w] == "." and (h+w)%2 == 0:
                for dh, dw in dhw:
                    h_new, w_new = h+dh, w+dw
                    if 0 <= h_new < H and 0 <= w_new < W:
                        if grid[h_new][w_new] == ".":
                            D.add_edge(h*W + w + 1, h_new*W + w_new + 1, 1)
    flow = D.max_flow(s, t)
    print(flow)
    for h in range(H):
        for w in range(W):
            if (h+w)%2 == 0:
                hw = h*W + w + 1
                for hw_new, cap, _ in D.adj[hw]:
                    if hw_new == s:
                        continue
                    if cap == 0:
                        h_new, w_new = divmod(hw_new - 1, W)
                        if h == h_new:
                            if w < w_new:
                                grid[h][w], grid[h][w_new] = "><"
                            else:
                                grid[h][w_new], grid[h][w] = "><"
                        else:
                            if h < h_new:
                                grid[h][w], grid[h_new][w] = "v^"
                            else:
                                grid[h_new][w], grid[h][w] = "v^"
    for h in range(H):
        print("".join(grid[h]))


if __name__ == '__main__':
    main()


Measured memory_bytes: 84884