#coding: utf-8
##yuki_192

def is_prime(n):
 if n==2 or n==3: return True
 if n%2==0 or n<2: return False
 for i in xrange(3,int(n**0.5)+1,2):
  if n%i==0:
   return False    
 return True

n=int(raw_input())

for x in xrange(n-100,n+101):
 if n<=100:
  break
 if n==101:
  print 4
  break
 if is_prime(x)==True:
  continue
 else:
  print x
  break