def main():
    N = int(input())
    import math
    def sieve_of_eratosthenes(n):
        prime = [True]*(n+1)
        prime[0] = False
        prime[1] = False

        sqrt_n = math.ceil(math.sqrt(n))
        for i in range(2, sqrt_n+1):
            if prime[i]:
                for j in range(2*i, n+1, i):
                    prime[j] = False
        prime = [i for i in range(2, n + 1) if prime[i]]
        return prime

    a = set()
    b = []
    num = sieve_of_eratosthenes(N)
    dp = [[-1]*N for _ in range(len(num))]
    dp[0][1] = 1
    a.add(2)
    b.append(2)
    for i in range(1, len(num)):
        for j in b:
            dp[i][j-1] = max(dp[i][j-1], dp[i-1][j-1])
            if j + num[i] <= N:
                dp[i][j+num[i]-1] = max(dp[i][j+num[i]-1], dp[i-1][j-1]+1)
                if j+num[i] not in a:
                    a.add(j+num[i])
                    b.append(j+num[i])
    print(dp[-1][N-1])
if __name__ == '__main__':
    main()