import sys,copy
import numpy as np
input=lambda:sys.stdin.readline().rstrip()
turn=np.array([[0,1],[-1,0]])
def search(B,pos,d,cnt):
	A=copy.copy(B)
	orig=[pos[0],pos[1]]
	while 1:
		for i in range(2):
			if A[(pos+d)[0]][(pos+d)[1]]==0:
				pos+=d
				A[pos[0]][pos[1]]=1
				cnt-=1
				break
			d=d@turn
		else:
			return cnt==0 and pos[0]==orig[0] and pos[1]==orig[1]
H,W=map(int,input().split())
A=np.array([[1 for j in range(W+2)] for i in range(H+2)])
ans,cnt=0,0
for i in range(H):
	S=input()
	for j in range(W):
		A[i+1][j+1]=(S[j]=='#')
		cnt+=(S[j]=='.')
if cnt>2*(H+W):
	print('NO')
	sys.exit()
for i in range(H):
	for j in range(W):
		if A[i+1][j+1]:
			continue
		d=np.array([1,0])
		for k in range(4):
			ans|=search(A,np.array([i+1,j+1]),d,cnt)
			d=d@turn
print(['NO','YES'][ans])