N=int(input())

if N==1:
    print(-1)
else:
    S=[1 for i in range(N+1)]
    
    S[0]=0
    S[1]=0
    
    for i in range(2,N+1):
        if S[i]==1:
            for j in range(2,N+1):
                if i*j>N:
                    break
                else:
                    S[i*j]=0
    #print(S[:100])
    s=[0]
    for i in range(len(S)):
        if S[i]==1:
            s.append(i)
    #print(s[:100])
    
    dp=[[[0,0] for i in range(N+1)]for j in range(len(s))]
    ans=(-1)
    for i in range(1,len(s)):
        for j in range(1,N+1):
            if j-s[i]<0:
                dp[i][j][0]=dp[i-1][j][0]
                dp[i][j][1]=dp[i-1][j][1]
            else:
                dp[i][j][0]=max(dp[i-1][j][0],dp[i-1][j-s[i]][0]+s[i])
                if dp[i][j][0]==dp[i-1][j][0]:
                    dp[i][j][1]=dp[i-1][j][1]
                else:
                    dp[i][j][1]=dp[i-1][j-s[i]][1]+1
                    if dp[i][j][0]==N:
                        if dp[i][j][1]>ans:
                            ans=dp[i][j][1]
    
    
    print(ans)