import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    ArrayList<Integer> prime = new ArrayList<Integer>();
    for(int i = 2; i <= N; i++) {
      boolean flg = true;
      for(int j = 2; j * j <= i; j++) {
        if(i % j == 0) {
          flg = false;
          break;
        }
      }
      if(flg) prime.add(i);
    }
    int num = prime.size();
    int ans = -1;
    if(num != 0) {
      // dp[i][j]はjを異なる素数の和で表す（素数0～素数iまでを用いる）場合の、最大の和の回数を表す
      int[][] dp = new int[num][N + 1];
      dp[0][2] = 1;
      for(int i = 1; i < num; i++) {
        for(int j = 2; j < N + 1; j++) {
          if(j >= prime.get(i)) {
            if(j - prime.get(i) == 0 || dp[i - 1][j - prime.get(i)] > 0) {
              dp[i][j] = Math.max(dp[i - 1][j], dp[i - 1][j - prime.get(i)] + 1);
            } else {
              dp[i][j] = dp[i - 1][j];
            }
          } else {
            dp[i][j] = dp[i - 1][j];
          }
        }
      }
      if(dp[num - 1][N] > 0) ans = dp[num - 1][N];
    }
    System.out.println(ans);
  }
}