s = input()
ans = "Yes"
for i, si in enumerate(s):
    if (i +1) % 2 == 0:
        if s[i] != " ":
            ans = 'No'
            break
    else:
        if ord(s[i]) < 97 or ord(s[i]) > 122:
            ans = 'No'
            break

print(ans)