import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int C = sc.nextInt();
		final int N = sc.nextInt();
		
		int[] arr = new int[N];
		for(int i = 0; i < N; i++){
			arr[i] = sc.nextInt();
		}
		
		int[] DP = new int[C + 1];
		Arrays.fill(DP, -1);
		DP[0] = 0;
		
		for(final int a : arr){
			for(int i = 0; i + a <= C; i++){
				if(DP[i] < 0){ continue; }
				if(DP[i + a] < 0 || (DP[i] + 1 < DP[i + a])){
					DP[i + a] = DP[i] + 1;
				}
			}
		}
		
		System.out.println(DP[C]);
		
	}

}