import collections
import random

def prime_sieve(n):
    # n以下の素数リスト(エラトステネスの篩)
    is_prime = [True for i in range(n + 1)]
    is_prime[0] = False
    is_prime[1] = False
    for i in range(4, n + 1, 2):
        is_prime[i] = False
    for i in range(3, int(n**0.5 + 1), 2):
        if is_prime[i]:
            for j in range(i * i, n + 1, i):
                is_prime[j] = False
    return [i for i in range(n + 1) if is_prime[i]]


def miller_rabin_test(n, k=100):
    if n == 2:
        return True
    if n < 2 or n & 1 == 0:
        return False
    d = (n - 1) >> 1
    while d & 1 == 0:
        d >>= 1
    for i in range(k):
        a = random.randint(1, n - 1)
        t = d
        y = pow(a, t, n)
        while t != n - 1 and y != 1 and y != n - 1:
            y = pow(y, 2, n)
            t <<= 1
        if y != n - 1 and t & 1 == 0:
            return False
    return True


N = int(input())
if N <= 46:
    primes = prime_sieve(N)
    maze = [i not in primes for i in range(N+1)]
    for w in range(3, N):
        dq = collections.deque()
        dq.append(1)
        visited = [False] * (N + 1)
        visited[1] = True
        while dq:
            v = dq.popleft()
            if v == N:
                break
            for d in [w, 1, -1, -w]:
                if 0 < v + d <= N and not visited[v + d] and maze[v + d]:
                    if d in [1, -1] and (v - 1) // w != (v - 1 + d) // w:
                        continue
                    dq.append(v + d)
                    visited[v + d] = True
        if visited[N]:
            print(w)
            exit()
else:
    if N % 8 == 1 and miller_rabin_test(N - 8):
        print(14)
    else:
        print(8)