#include "bits/stdc++.h"
using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define array2(type, x, y) array<array<type, y>, x>
#define vector2(type) vector<vector<type> >
#define out(...) printf(__VA_ARGS__)

int dxy[] = {0, 1, 0, -1, 0};

void solve();
signed main()
{
#if DEBUG
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

/*================================*/
#if DEBUG
#define SIZE 41234
#else
#define SIZE 41234
#endif

int N,M,Q;
int DP[SIZE];
vector<int> primes;

void solve() {
    cin>>N;
    REP(i,SIZE)DP[i]=-1;
    FOR(i,2,N+1) {
        bool is_prime = true;
        for (int p:primes) if (i%p==0) {
            is_prime = false;
            break;
        }
        if (!is_prime) continue;
        primes.push_back(i);
        RREP(j,N+1) if (DP[j]>0){
            DP[j+i] = max(DP[j+i], DP[j]+1);
        }
        DP[i] = max(DP[i], 1LL);
    }
    
    cout << DP[N] << endl;
}