N=int(input())

SO=[1 for i in range(N+1)]
SO[0]=0
SO[1]=0
for i in range(2,N+1):
    if SO[i]==1:
        for j in range(2,N+1):
            if i*j>N:
                break
            else:
                SO[i*j]=0
#print(SO)
L=[]
for i in range(len(SO)):
    if SO[i]==1:
        L.append(i)
#print(L)
dp=[-1 for i in range(N+1)]
dp[0]=0
for i in range(len(L)):
    for j in range(N+1):
        if L[i]<=j and dp[N-j]>=0:
            if dp[N-j+L[i]]<dp[N-j]+1:
                dp[N-j+L[i]]=dp[N-j]+1
print(dp[N])