# your co
s=input()
a=[]
a.append(s[0])
for i in range(2,len(s)):
if i%2==0:
a.append(s[i])
a.sort()
for i in range(len(a)):
print(a[i]+"+")
IyB5b3VyIGNvCnM9aW5wdXQoKQphPVtdCmEuYXBwZW5kKHNbMF0pCmZvciBpIGluIHJhbmdlKDIsbGVuKHMpKToKCWlmIGklMj09MDoKCQlhLmFwcGVuZChzW2ldKQphLnNvcnQoKQpmb3IgaSBpbiByYW5nZShsZW4oYSkpOgoJcHJpbnQoYVtpXSsiKyIp