def Eratosthenes(n):
    is_prime=[True] * (n+1)
    is_prime[0]=False
    is_prime[1]=False
    for i in range(2,int(n**0.5)+1):
        if not is_prime[i]:
            continue
        for j in range(i*2,n+1,i):
            is_prime[j]=False
    return [i for i in range(n+1) if is_prime[i]]

def main():
    n=int(input())
    lis=Eratosthenes(n)
    N=len(lis)
    dp=[[-1]*(n+1) for _ in range(1+N)]
    dp[0][0]=0
    for i in range(N):
        num=lis[i]
        for j in range(n+1):
            if dp[i][j]<0:
                continue
            if j+num<=n:
                dp[i+1][j+num]=max(dp[i+1][j+num],dp[i][j]+1)
            dp[i+1][j]=max(dp[i+1][j],dp[i][j])
    print(dp[N][n])
if __name__=='__main__':
    main()