#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    int L, N, ans=1e9;
    cin >> L >> N;
    vector<int> x(N+1);
    for (int i=1; i<=N; i++) cin >> x[i];

    vector dp(N+1, vector(L+1, vector<bool>(2)));
    dp[0][0][0] = 1;
    for (int i=1; i<=N; i++){
        for (int j=0; j<=L; j++){
            if (j-(x[i]-x[i-1])>=0){
                dp[i][j][0] = dp[i][j][0] | dp[i-1][j-(x[i]-x[i-1])][0];
                dp[i][j][1] = dp[i][j][1] |  dp[i-1][j-(x[i]-x[i-1])][0];
            }
            dp[i][j][0] = dp[i][j][0] | dp[i-1][j][1];
            dp[i][j][1] = dp[i][j][1] | dp[i-1][j][1];
        }
    }

    for (int i=0; i<=L; i++){
        if (dp[N][i][0]) ans = min(ans, abs(i-(L-i)));
    }

    cout << ans << endl;

    return 0;
}