import math
N=int(input())
S=[]

maxv=N+10
def eratos(n):
    isprime=[True]*(n+1)
    isprime[0]=False
    isprime[1]=False
    for i in range(2,int(math.sqrt(n))+1):
        if isprime[i]==True:
            j=i+i
            while j<=n:
                isprime[j] =False
                j=j+i

    for i in range(n+1):
        if isprime[i]==True:
            S.append(i)
    return S
    
sosu=eratos(N)
#print(sosu)
#print(len(sosu))


DP = [[-1]*(maxv) for i in range(len(S)+1)] 
for i in range(len(S)+1):
    DP[i][0]=0

for i in range(len(S)):
    for j in range(maxv):
        if  j+S[i]<=N and DP[i][j]!=-1:
            DP[i+1][j+S[i]]=DP[i][j]+1
          
        DP[i+1][j]=max(DP[i][j],DP[i+1][j])

ans=-1
for i in range(len(S)+1):
    if DP[i][N]>ans:
        ans=DP[i][N]
if ans>0:
    
    print(ans)
else:
    print(-1)

#print(DP)