#include <bits/stdc++.h>

using namespace std;

int main() {
    int n, i, j;
    cin >> n;
    int t[n + 1] = {};
    vector<int> sosuu;
    for(i = 2; i * i <= n; i++) {
        if(t[i] == 0) {
            sosuu.push_back(i);
            for(j = i * i; j <= n; j += i) {
                t[j] = 1;
            }
        }
    }
    for(; i <= n; i++) {
        if(t[i] == 0) sosuu.push_back(i);
    }

    int ss = sosuu.size();
    int dp[ss + 1][n + 1];
    for(i = 0; i <= ss; i++) {
        for(j = 0; j <= n; j++) {
            dp[i][j] = -1;
        }
    }

    dp[0][0] = 0;

    for(i = 0; i < ss; i++) {
        for(j = 0; j <= n; j++) {
            if(j - sosuu[i] >= 0 && dp[i][j - sosuu[i]] != -1) {
                dp[i + 1][j] = max(dp[i][j], dp[i][j - sosuu[i]] + 1);
            } else {
                dp[i + 1][j] = dp[i][j];
            }
        }
    }

    cout << dp[ss][n] << endl;
    return 0;
}