//#include #include #include #include #include #include #include #include #define rep(i,n) for(ll i = 0; i < n; i++) //[0,n) #define srep(i,a,b) for(ll i = a; i < b; i++) //[a,b) #define arep(i,a,b,d) for(ll i = a; i < b; i += d) #define all(A) (A).begin(),(A).end() #define rall(A) (A).rbegin(),(A).rend() #define pmt(A) next_permutation(all(A)) using namespace std; using ll = long long; using ull = unsigned long long; using P = pair; using pq = priority_queue,greater>; const ll inf = 1LL<<60; const int iinf = (int)1e9+1; const int mod9 = 998244353; const int mod1 = 1000000007; struct Edge { int to; long long cost; int from; }; bool compe(const Edge &e,const Edge &e2){ return e.cost < e2.cost; } using Graph = vector>; using SGraph = vector>; template int siz(T& a){return (int)a.size();} ll squa(ll a){ return a*a; } ll mceil(ll a,ll b){ return (a+b-1)/b; } int dp[3000][20202]; int main(void){ int N; cin >> N; vector isprime(20001,1); isprime[0] = isprime[1] = 0; srep(i,2,20000+1){ if(!isprime[i]) continue; for(int j = 2*i; j <= 20000; j += i) isprime[j] = 0; } vector pr; rep(i,20000+1) if(isprime[i]) pr.push_back(i); rep(i,2500) rep(j,20202) dp[i][j] = -1; int n = siz(pr); dp[0][0] = 0; rep(i,n){ for(int j = N; j >= 0; j--){ if(dp[i][j] == -1) continue; dp[i+1][j] = max(dp[i+1][j],dp[i][j]); dp[i+1][j+pr[i]] = max(dp[i+1][j+pr[i]],dp[i][j]+1); } } cout << (dp[n][N] <= 0 ? -1 : dp[n][N]); }