using namespace std;
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<cmath>
int N;
int dp[20009];
vector<int> p(20009);
int fanc(int i, vector<int> p) {
	if (dp[i] != -1) {
		return dp[i];
	}
	int res = -1;
	if (i == 0) res = 0;
	for (int j = 2; j <= N; j++) {
		if (p[j]==1 and (i - j) >= 0) {
			p[j] = 0;
			if (res < fanc(i - j,p) + 1) {
				if (fanc(i - j,p) == -1) {
					res = -1;
				}
				else {
					res = fanc(i - j, p) + 1;
				}
			}
		}
	}
	return dp[i] = res;
}

int main() {
	cin >> N;
	for (int j = 2; j <= N; j++) {
		for (int k = 2; k <= int(sqrt(j)); k++) {
			if (j % k == 0 and j != k) {
				p[j] = -1;
				break;
			}
		}
		if (p[j] != -1) {
			p[j] = 1;
		}
	}
	memset(dp, -1, sizeof(dp));
	cout << fanc(N,p) << endl;
}