N = int( input() )
ans = 0
for i in range( 1, int( 1e6 ), 1 ):
  ng = False
  q = i * int( 1e9 + 1 )
  if q > N: break
  f = str( q )
  for j in range( len( f ) ):
    ng |= f[ j ] != f[ len( f ) - 1 - j ]
  ans += not ng
print( ans )