#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


void solve(){
    ll L, N; cin >> L >> N;
    vector<ll> X(N+1);
    for(ll i=1; i<=N; i++) cin >> X[i];

    vector<ll> Y(N+1);
    Y[1] = X[1];
    for(ll i=2; i<=N; i++) Y[i] = X[i]-X[i-1];

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

    ll ans = LINF;
    for(ll j=0; j<=L; j++) if(dp[N][j]) ans = min(ans, abs(2*j-L));

    cout << ans << endl;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}