#include<stdio.h>
#include<stdlib.h>

#define MAX(a,b) ((a)<(b)?(b):(a))

void run(void){
  int n;
  scanf("%d",&n);
  if(n<=2){
    printf("%d\n",n==1?-1:1);
    return;
  }
  char *isPrime=(char *)calloc(n+1,sizeof(char));
  int i;
  isPrime[2]=1;
  for(i=3;i<=n;i++){
    isPrime[i]=i%2;
  }
  for(i=3;i*i<=n;i+=2){
    if(isPrime[i]){
      int j;
      for(j=i*i;j<=n;j+=2*i){
        isPrime[j]=0;
      }
    }
  }

  int *ans=(int *)calloc(n+1,sizeof(int));
  ans[2]=1;
  int up=2;
  for(i=3;i<=n;i+=2){
    if(isPrime[i]){
      int j;
      for(j=(i+up)>n?n:(i+up);j>i;j--){
        ans[j]=MAX(ans[j],(ans[j-i]>0)*(ans[j-i]+1));
      }
      ans[i]=MAX(ans[i],1);
      up+=i;
    }
  }
  printf("%d\n",ans[n]==0?-1:ans[n]);
  return;
}

int main(void){
  run();
  return 0;
}