def primes(n):
    memo = [True] * (n + 1)
    i = 2
    while i * i <= n:
        if memo[i]:
            j = i << 1
            while j <= n:
                memo[j] = False
                j += i
        i += 1
    return {i for i in range(n + 1) if memo[i] and i >= 2}


N = int(input())

P = primes(N + 100)

l, r = N - 100, N + 100
for i in range(l, r + 1):
    if i != 1 and i not in P:
        print(i)
        quit()