import java.io.*;
import java.util.*;


public class Main_yukicoder385 {

    public static void main(String[] args) {
    	Scanner sc = new Scanner(System.in);
    	Printer pr = new Printer(System.out);

    	final int INF = Integer.MIN_VALUE;

    	int m = sc.nextInt();
    	int n = sc.nextInt();

    	int[] c = new int[n];
    	for (int i = 0; i < n; i++) {
    		c[i] = sc.nextInt();
    	}

    	int[] dp = new int[m + 1];
    	Arrays.fill(dp, INF);
    	dp[0] = 0;
    	for (int i = 0; i < n; i++) {
    		for (int cn = c[i], cnn = 1; cn <= m; cn *= 2, cnn++) {
    			for (int j = 0; j <= m; j++) {
    				if (dp[j] == INF) {
    					continue;
    				}
    				if (j + cn > m) {
    					continue;
    				}
    				dp[j + cn] = Math.max(dp[j + cn], dp[j] + cnn);
    			}
    		}
    	}

    	Prime prime = new Prime(m);

    	int ret = 0;
    	int max = 0;
    	for (int i = 1; i <= m; i++) {
    		if (dp[i] != INF && prime.isPrime(m - i)) {
    			ret += dp[i];
    		}
    		max = Math.max(max, dp[i]);
    	}

    	ret += max;

    	pr.println(ret);

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Prime {
		private int n;
		private List<Integer> primes;
		private BitSet p;

		Prime(int n) {
			this.n = n;

			p = new BitSet(n / 2);
			int m = (int)Math.sqrt(n);

			for (int i = 1; i <= m; i++) {
				if (p.get(i - 1)) {
					continue;
				}

				for (int j = 2 * i * (i + 1); 2 * j + 1 <= n; j += 2 * i + 1) {
					p.set(j - 1);
				}
			}
		}

		boolean isPrime(int n) {
			if (n == 2) {
				return true;
			}

			if (n == 1 || (n & 0x1) == 0) {
				return false;
			}

			return !p.get(n / 2 - 1);
		}

		List<Integer> getPrimeList() {
			if (primes != null) {
				return primes;
			}

			primes = new ArrayList<>();
			if (n >= 2) {
				primes.add(2);
				for (int i = 1; 2 * i + 1 <= n; i++) {
					if (!p.get(i - 1)) {
						primes.add(2 * i + 1);
					}
				}
			}

			return primes;
		}

		private static boolean isPrime(long n) {
			if (n == 2) {
				return true;
			}

			if (n == 1 || (n & 0x1) == 0) {
				return false;
			}

			for (long i = 3; i * i <= n; i += 2) {
				if (n % i == 0) {
					return false;
				}
			}

			return true;
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}