import string

txt = string.ascii_lowercase
S = input()

for i in range(len(S) // 2 + 1):
  if len(S) > i * 2 + 1:
    if not(S[i*2] in txt):
      print('No')
      break
  
  if len(S) > i * 2 + 1 + 1:
    if not(S[i*2+1] == ' '):
      print('No')
      break
else:
  print('Yes')