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