from typing import NamedTuple, Optional, List, cast # https://github.com/not522/ac-library-python/blob/master/atcoder/maxflow.py class MFGraph: class Edge(NamedTuple): src: int dst: int cap: int flow: int class _Edge: def __init__(self, dst: int, cap: int) -> None: self.dst = dst self.cap = cap self.rev: Optional[MFGraph._Edge] = None def __init__(self, n: int) -> None: self._n = n self._g: List[List[MFGraph._Edge]] = [[] for _ in range(n)] self._edges: List[MFGraph._Edge] = [] def add_edge(self, src: int, dst: int, cap: int) -> int: assert 0 <= src < self._n assert 0 <= dst < self._n assert 0 <= cap m = len(self._edges) e = MFGraph._Edge(dst, cap) re = MFGraph._Edge(src, 0) e.rev = re re.rev = e self._g[src].append(e) self._g[dst].append(re) self._edges.append(e) return m def get_edge(self, i: int) -> Edge: assert 0 <= i < len(self._edges) e = self._edges[i] re = cast(MFGraph._Edge, e.rev) return MFGraph.Edge( re.dst, e.dst, e.cap + re.cap, re.cap ) def edges(self) -> List[Edge]: return [self.get_edge(i) for i in range(len(self._edges))] def change_edge(self, i: int, new_cap: int, new_flow: int) -> None: assert 0 <= i < len(self._edges) assert 0 <= new_flow <= new_cap e = self._edges[i] e.cap = new_cap - new_flow assert e.rev is not None e.rev.cap = new_flow def flow(self, s: int, t: int, flow_limit: Optional[int] = None) -> int: assert 0 <= s < self._n assert 0 <= t < self._n assert s != t if flow_limit is None: flow_limit = cast(int, sum(e.cap for e in self._g[s])) current_edge = [0] * self._n level = [0] * self._n def fill(arr: List[int], value: int) -> None: for i in range(len(arr)): arr[i] = value def bfs() -> bool: fill(level, self._n) queue = [] q_front = 0 queue.append(s) level[s] = 0 while q_front < len(queue): v = queue[q_front] q_front += 1 next_level = level[v] + 1 for e in self._g[v]: if e.cap == 0 or level[e.dst] <= next_level: continue level[e.dst] = next_level if e.dst == t: return True queue.append(e.dst) return False def dfs(lim: int) -> int: stack = [] edge_stack: List[MFGraph._Edge] = [] stack.append(t) while stack: v = stack[-1] if v == s: flow = min(lim, min(e.cap for e in edge_stack)) for e in edge_stack: e.cap -= flow assert e.rev is not None e.rev.cap += flow return flow next_level = level[v] - 1 while current_edge[v] < len(self._g[v]): e = self._g[v][current_edge[v]] re = cast(MFGraph._Edge, e.rev) if level[e.dst] != next_level or re.cap == 0: current_edge[v] += 1 continue stack.append(e.dst) edge_stack.append(re) break else: stack.pop() if edge_stack: edge_stack.pop() level[v] = self._n return 0 flow = 0 while flow < flow_limit: if not bfs(): break fill(current_edge, 0) while flow < flow_limit: f = dfs(flow_limit - flow) flow += f if f == 0: break return flow def min_cut(self, s: int) -> List[bool]: visited = [False] * self._n stack = [s] visited[s] = True while stack: v = stack.pop() for e in self._g[v]: if e.cap > 0 and not visited[e.dst]: visited[e.dst] = True stack.append(e.dst) return visited def main(): h, w = map(int, input().split()) S = [input() for _ in range(h)] rocks = [] holes = [] for r in range(h): for c, x in enumerate(S[r]): if x == 'r': rocks.append((r, c)) if x == 'h': holes.append((r, c)) from bisect import bisect_left def rix(r, c): return bisect_left(rocks, (r, c)) def hix(r, c): return bisect_left(holes, (r, c)) + n n = len(rocks) m = len(holes) s = n + m t = s + 1 G = MFGraph(t + 1) for v in range(n): G.add_edge(s, v, 1) for v in range(m): G.add_edge(n + v, t, 1) for r in range(h): for it in [range(w), reversed(range(w))]: prv = -1 for c in it: if S[r][c] == 'r' and prv != -1: G.add_edge(rix(r, c), hix(r, prv), 1) if S[r][c] == 'h': prv = c for c in range(w): for it in [range(h), reversed(range(h))]: prv = -1 for r in it: if S[r][c] == 'r' and prv != -1: G.add_edge(rix(r, c), hix(prv, c), 1) if S[r][c] == 'h': prv = r f = G.flow(s, t) print('Yes' if f == n else 'No') main()