#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <math.h>
using namespace std;
int N;
vector<vector<int>> dp;
int idx = 0;
bool is_prime(int num)
{
	if (num < 2) return false;
	else if (num == 2) return true;
	else if (num % 2 == 0) return false; // 偶数はあらかじめ除く
	double sqrtNum = sqrt(num);
	for (int i = 3; i <= sqrtNum; i += 2)
	{
		if (num % i == 0)
		{
			return false;
		}
	}
	return true;
}
int main(void) 
{
	cin >> N;
	dp.push_back(vector<int>(N + 1, 0));
	++dp[idx][2];
	for (int i = 3; i <= N; ++i) {
		if (is_prime(i)) {
			++idx;
			dp.push_back(vector<int>(N + 1, 0));
			for (int j = 0; j <= N; ++j) {
				if (dp[idx - 1][j] != 0) {
					dp[idx][j] = dp[idx - 1][j];
					if (N < j + i) continue;
					dp[idx][j + i] = max(dp[idx][j + i], dp[idx - 1][j] + 1);
				}
			}
			dp[idx][i] = max(dp[idx][i], 1);
		}
	}
	if (dp[idx][N] == 0) dp[idx][N] = -1;
	cout << dp[idx][N] << endl;
	return 0;
}