def f(s,n):
 r=n
 for i in s:
  for j in s:
   p,q=s.split(i,1);a=p+q.replace(j,'',2)
   if len(s)-len(a)>2and'0'<i!=j:r=max(r,f(a,n+int(i+j+j)))
 return r
print(f(input(),0))