S = [input() for _ in range(3)]
se = [set() for _ in range(2)]
for i in range(3):
    for j in range(3):
        se[(i + j) & 1].add(S[i][j])
if len(se[0]) == 1 and len(se[1]) == 1:
    print("Yes")
else:
    print("No")