import sympy


N = int(input())
# 2～29の範囲内の素数を返すジェネレータ
p_g = sympy.primerange(2, N+1)

p_list = list(p_g)

def min_num_part_sum(a, A):
    # 初期化
    N = len(a)
    inf = float(-100)
    dp = [[inf for i in range(A + 1)] for j in range(N + 1)]
    dp[0][0] = 0

    # DP
    for i in range(N):
        for j in range(A + 1):
            if a[i] <= j:  # i+1番目の数字a[i]を足せるかも
                dp[i + 1][j] = max(dp[i][j - a[i]] + 1, dp[i][j])
            else:  # 入る可能性はない
                dp[i + 1][j] = dp[i][j]
    return dp[N][A]

print(min_num_part_sum(p_list,N))