#pragma region Macros

#include <bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;
// using namespace __gnu_cxx;

#define TO_STRING(var) # var
#define pb emplace_back
#define int ll
#define endl '\n'

using ll = long long;
using ld = long double;
const ld PI = acos(-1);
const ld EPS = 1e-10;
const int INF = 1 << 30;
const ll INFL = 1LL << 62;
const int MOD = 998244353;
// const int MOD = 1000000007;

int ceil(int x, int y) {return (x > 0 ? (x + y - 1) / y : x / y);}
int POW(int x, int y) {
    if (y != (int)(y) or y < 0 or x != 0 && x != 1 && y > 64) {cout << "Error" << endl;return 0;}
    if (y == 0) return 1;
    if (y % 2 == 0) return POW(x * x, y / 2);
    return x * POW(x, y - 1);
}

__attribute__((constructor))
void constructor() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
}

#pragma endregion

vector<int> erat(int n) {

	vector<bool> prime(n + 1, true);
	prime[0] = false;
	if (n >= 1) prime[1] = false;

	for (int i = 2; i * i <= n; i++) {
		if (prime[i]) {
			for (int j = i + i; j <= n; j += i) {
				prime[j] = false;
			}
		}
	}

	vector<int> ret;
	for (int i = 2; i <= n; i++) {
		if (prime[i]) ret.pb(i);
	}
	return ret;
}

signed main() {
    int N;
	cin >> N;

	vector<int> p = erat(N);
	int sz = p.size();
	vector<vector<int>> dp(sz + 1,vector<int>(40000, -1));
	dp[0][0] = 0;
	for (int i = 0; i < sz; i++) {
		for (int j = 0; j <= N; j++) {
			if (dp[i][j] == -1) continue;
			dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
			dp[i + 1][j + p[i]] = max(dp[i + 1][j + p[i]], dp[i][j] + 1);
		}
	}

	cout << dp[sz][N] << endl;

}