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