#yuki_491

n=int(raw_input())
n/=1000000001
res=0
for i in xrange(1,10**5):
 v=s=t=str(i)
 v=v[::-1]
 s+=v
 t+=v[1:len(v)]
 if int(s)<=n:
  res+=1
 if int(t)<=n:
  res+=1
print res