s = [input() for _ in range(3)]
c = s[0][0]
ok = True
for i in range(3):
    for j in range(3):
        if (i + j) % 2 == 0:
            if s[i][j] != c:
                ok = False
        else:
            if s[i][j] == c:
                ok = False

print('Yes' if ok else 'No')