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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int length = sc.nextInt();
        int n = sc.nextInt();
        int[] values = new int[n + 1];
        values[0] = sc.nextInt();
        int sum = values[0];
        for (int i = 1; i < n; i++) {
            values[i] = sc.nextInt() - sum;
            sum += values[i];
        }
        values[n] = length - sum;
        boolean[][] dp = new boolean[n][length];
        int max = Math.abs(values[n] - values[0]);
        dp[0][max] = true;
        for (int i = 1; i < n; i++) {
            for (int j = max; j >= 0; j--) {
                if (dp[i - 1][j]) {
                    dp[i][j + values[i]] = true;
                    dp[i][Math.abs(j - values[i])] = true;
                }
            }
            max += values[i];
        }
        for (int i = 0; ;i++) {
            if (dp[n - 1][i]) {
                System.out.println(i);
                return;
            }
        }
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}