import sys def I(): return int(sys.stdin.readline().rstrip()) def MI(): return map(int,sys.stdin.readline().rstrip().split()) def LI(): return list(map(int,sys.stdin.readline().rstrip().split())) def LI2(): return list(map(int,sys.stdin.readline().rstrip())) def S(): return sys.stdin.readline().rstrip() def LS(): return list(sys.stdin.readline().rstrip().split()) def LS2(): return list(sys.stdin.readline().rstrip()) def is_prime(n): # ミラー・ラビン素数判定法 d = n-1 d //= d & (-d) A = [2,3,5,7,11,13,17,19,23,29,31,37] for a in A: e = d x = pow(a,e,n) if x == 1: continue while x != n-1: x = x**2 % n if x == 1 or e == n-1: return False e <<= 1 return True N = I() if N == 4: ans = 3 elif N == 6: ans = 5 elif N in [8,9,10,15,16,22]: ans = 7 elif N == 12: ans = 11 elif N == 14: ans = 13 elif N == 20 or N == 21: ans = 19 elif N == 24 or N == 25: ans = 23 else: if N % 8 == 1 and is_prime(N-8): ans = 14 else: ans = 8 print(ans)