#include <bits/stdc++.h>
using namespace std;

vector<bool> is_prime( 1000100 );
vector<int> Eratosthenes( const int N = 1000100 ) {
    for( int i = 0; i <= N; i++ ) {
        is_prime[ i ] = true;
    }
    vector<int> P;
    for( int i = 2; i <= N; i++ ) {
        if( is_prime[ i ] ) {
            for( int j = 2 * i; j <= N; j += i ) {
                is_prime[ j ] = false;
            }
            P.emplace_back( i );
        }
    }
    return P;
}

vector<int> ps;
int dp[2270][20005];

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

    Eratosthenes();
    for (int i = 2; i <= N; i++) {
        if (is_prime[i]) {
            ps.push_back(i);
        }
    }

    memset(dp, -1, sizeof(dp));

    

    for (int i = 0; i < 2270; i++) {
        dp[i][0] = 0;
    }

    for (int i = 1; i <= ps.size(); i++) {
        for (int j = 1; j <= N; j++) {
            dp[i][j] = max(dp[i][j], dp[i - 1][j]);
            if (j - ps[i - 1] >= 0 && dp[i - 1][j - ps[i - 1]] != -1) {
                dp[i][j] = max(dp[i][j], dp[i - 1][j - ps[i - 1]] + 1);
            }
        }
    }

   
    cout << dp[ps.size()][N] << endl;
    return 0;
}