s = input()

flag = 1
for i in range(len(s)):
    if i % 2 == 0:
        if 97 > ord(s[i]) or ord(s[i]) > 123:
            flag = 0
            break
    elif i % 2 == 1:
        if s[i] != ' ':
            flag = 0
            break
            
if(flag):
    print('Yes')
else:
    print('No')