#50311: python笨方法
def aa(s):
結果 = ''
for c in s:
if ('A' <= c <= 'Z') or ('a' <= c <= 'z'):
結果 += c
return 結果
def bb(s):
字典 = {}
for c in s:
if c in 字典:
字典[c] += 1
else:
字典[c] = 1
奇數次 = 0
for 次數 in 字典.values():
if 次數 % 2 != 0:
奇數次 += 1
if 奇數次 <= 1:
return 'yes !'
else:
return 'no...'
while True:
try:
S=list(aa(input('')).lower())
print(bb(S))
except EOFError:
break