import sys
from copy import deepcopy

sys.setrecursionlimit(10 ** 6)

def main():
    h, w = map(int, input().split())
    t0 = [[-1 if c == "#" else 0 for c in input()] for _ in range(h)]
    for di in range(h):
        for dj in range(-w + 1, w):
            flag = True
            t = deepcopy(t0)
            br = False
            for i in range(h):
                for j in range(w):
                    if t[i][j] != -1: continue
                    t[i][j] = 1
                    if i + di >= h or j + dj >= w or j + dj < 0 or t[i + di][j + dj] != -1:
                        br = True
                        break
                    flag = False
                    t[i + di][j + dj] = 2
                if br: break
            if br or flag: continue
            print("YES")
            exit()
    print("NO")

main()