def f(s,n):
 r=n
 for i in{*s}:
  p,q=s.split(i,1)
  for j in s:
   if'0'<i!=j!=q.count(j)>1:r=max(r,f(p+q.replace(j,'',2),n+int(i+j+j)))
 return r
print(f(input(),0))