Lab

lab = raw_input()
N = len (lab)
i = 1
lab = list (lab)
while i < N :
    mas = raw_input()
    mas = list (mas)
    lab += mas
    i += 1
mas = (0,) * N * N
stack = []
i = 0
stack.append(i)
mas = list(mas)
while stack != [] :
    i = stack[0]
    stack.pop(0)
    mas[i] = 1
    if i + 1 == N * N - 1 :
        mas[i+1] = 1
        break
    else :
        if i + 1 < N * N - 1 and lab[i+1] == '.' and mas[i+1] == 0 :
            stack.append(i + 1)
    if i + N == N * N - 1 :
        mas[i+N] = 1
        break
    else :
        if i + N < N * N - 1 and lab[i+N] == '.' and mas[i+N] == 0 :
            stack.append(i + N)
if mas[N * N - 1] == 0 :
    print'NO'
else :
    print'YES'