#coding: utf-8
#yuki_312

def prime_decomp(n):
  i = 2
  table = []
  while i * i <= n:
    while n % i == 0:
      n /= i
      table.append(i)
    i += 1
  if n > 1:
    table.append(n)
  return table

n=int(raw_input())
s=prime_decomp(n)

if s[-1]==2:
 print 4
elif s[0]==2 and s[1]==2:
 if s[2]<4:
  print 3
 else:
  print 4
elif s[0]==2:
 i=0
 while s[i]==2:
  i+=1
  continue
 print s[i]
else:
 print s[0]