s=input();l=len(s);r=range
def f(v,u,c):
 m=c
 for i in r(l):
  for j in r(i+1,l):
   for k in r(j+1,l):
    if s[i]!='0'and s[j]==s[k]and s[i]!=s[j]:m=max(m,f(s[:i]+s[i+1:j]+s[j+1:k],u,c+int(s[i]+s[j]+s[k])))
 return m
print(f(s,[0]*l,0))