N,M=map(int,raw_input().split())
A=[raw_input() for i in range(N)]
dir=[(1,0),(0,1),(-1,0),(0,-1)]
sur=[(-1,-1),(1,1),(1,-1),(-1,1),(1,0),(0,1),(-1,0),(0,-1)]
cnt=0 
for i in range(N):
    for j in range(M):
        if A[i][j]=='.':
            cnt+=1
        if i>0 and i+1<N and j>0 and j+1<M:
            ng=True
            for (a,b) in sur:
                if A[i+a][j+b]!='.':
                    ng=False
                    break
            if ng:
                print "NO"
                exit()
for i in range(N):
    for j in range(M):
        if A[i][j] =='.':
            for k in range(len(dir)):
                arrived=[[False for m in range(M)]for n in range(N)]
                a,b=i,j
                curCnt = 0
                arrived[a][b]=True
                #print (a,b),
                for d in range(6):
                    na,nb=a+dir[(k+d)%4][0],b+dir[(k+d)%4][1]
                    ok = False
                    while na<N and na >=0 and nb <M and nb>=0 and A[na][nb]=='.' and (arrived[na][nb]==False or (i== na and j==nb)):
                            curCnt+=1
                            #print (na,nb) ,
                            arrived[na][nb]=True
                            a=na
                            b=nb
                            ok=True
                            if a==i and b==j:
                                break
                            na,nb=a+dir[(k+d)%4][0],b+dir[(k+d)%4][1]
                    if ok == False or (a==i and b==j ):
                        break
                #print 
                if a==i and b==j and cnt == curCnt:
                    print "YES"
                    exit()
print "NO"