#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, x> #define vector2(type) vector > #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 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; }