def g(s,t):
 r=''
 for i in s:
  if t and i==t[0]:t=t[1:]
  else:r+=i
 return'e'if t else r
def f(s,n):
 r=n
 for i in range(1,10):
  for j in range(10):
   x=i*100+j*10+j;a=g(s,str(x))
   if i-j and a!='e':r=max(r,f(a,n+x))
 return r
print(f(input(),0))