#include<stdio.h>

int main(void){
	int p[32768]={0},i,j,n,m[32768]={0};
	for(i = 2;i <= 185;i++){if(!p[i]){for(j = 2*i;j <= 20000;j+=i){p[j]=1;}}}
	for(i = 2;i <= 20000;i++){
		if(!p[i]){
			for(j = 25000-i;j >= 0;j--){
				if(j == 0 || m[j] != 0){
					if(m[j] + 1 > m[j+i]){m[j+i] = m[j]+1;}
				}
			}
		}
	}
	scanf("%d",&n);
	if(m[n]){printf("%d\n",m[n]);}else{printf("-1\n");}
	return 0;
}