h, w = map(int, input().split())
S = ["#" * (w + 2)] + ["#" + input() + "#" for _ in range(h)] + ["#" * (w + 2)]
used = [[False] * (w + 2) for _ in range(h + 2)]
cc = sum(row.count('.') for row in S)

di = [0, -1, 0, 1]
dj = [1, 0, -1, 0]

for i in range(1, h + 1):
    for j in range(1, w + 1):
        if S[i][j] == '#':
            continue
        
        for k in range(4):
            lst = []
            ii = i
            jj = j
            cnt = 0
            t = k
            while not used[ii][jj]:
                cnt += 1
                used[ii][jj] = True
                lst.append((ii, jj))
                ni = ii + di[t]
                nj = jj + dj[t]
                if S[ni][nj] == '.':
                    ii, jj = ni, nj
                    continue
                t = (t + 1) % 4
                ni = ii + di[t]
                nj = jj + dj[t]
                if S[ni][nj] == '.':
                    ii, jj = ni, nj
                    continue
                else:
                    break

            if cnt == cc and ii == i and jj == j:
                print("YES")
                exit()

            for ii, jj in lst:
                used[ii][jj] = False

print("NO")