import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		boolean[] isNotPrime = new boolean[n + 1];
		TreeMap<Integer, Integer> map = new TreeMap<>();
		map.put(0, 0);
		for (int i = 2; i <= n; i++) {
		    if (!isNotPrime[i]) {
		        for (int j = 2; j * i <= n; j++) {
		            isNotPrime[j * i] = true;
		        }
		        Integer x = n + 1;
		        while ((x = map.lowerKey(x)) != null) {
		            int value = map.get(x);
		            if (x + i <= n && (!map.containsKey(x + i) || map.get(x + i) <= value)) {
		                map.put(x + i, value + 1);
		            }
		        }
		    }
		}
		if (!map.containsKey(n)) {
		    System.out.println(-1);
		} else {
		    System.out.println(map.get(n));
		}
	}
}