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)