#include<bits/stdc++.h>
int prime[20001];
int p[2262];
int dp[2263][20001];
main(){
    for(int i = 2;i*i <= 20000;i++){
        if(prime[i])continue;
        for(int j = i*2;j <= 20000;j+=i){
            prime[j] = 1;
        }
    }
    int count = 0;
    for(int i = 2;i <= 20000;i++){
        if(prime[i])continue;
        p[count] = i;
        count++;
    }
    for(int i = 0;i < 2262;i++){
        for(int j = 0;j <= 20000;j++){
            dp[i+1][j] = dp[i][j];
            if(j < p[i])continue;
            if(j-p[i]==0){
                dp[i+1][j] = std::max(dp[i][j],1);
            }else if(dp[i][j-p[i]]!=0){
                dp[i+1][j] = std::max(dp[i][j],dp[i][j-p[i]]+1);
            }
        }
    }
    int N;
    scanf("%d",&N);
    printf("%d\n",dp[2262][N]?dp[2262][N]:-1);
}