#include <bits/stdc++.h>

#define f first
#define s second
#define pb push_back
#define mp make_pair

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;

const int N = 300500, inf = 1e9, mod = 998244353;
const ll INF = 1e18;

int sum(int a, int b) {
    a += b;
    if (a >= mod)
        a -= mod;
    return a;
}

int sub(int a, int b) {
    a -= b;
    if (a < 0)
        a += mod;
    return a;
}

int mult(int a, int b) {
    return 1ll * a * b % mod;
}

int bp(int a, int b) {
    int res = 1;
    while (b) {
        if (b & 1)
            res = mult(res, a);
        a = mult(a, a);
        b >>= 1;
    }
    return res;
}

int inv(int x) {
    return bp(x, mod - 2);
}

int dp[200000];
int dp2[200000];

void solve() {
    int b, n;
    cin >> b >> n;
    vector<int> a(n);
    for (int i=0;i<n;i++) cin >> a[i];
    for (int i=0;i<=n*b;i++) dp[i] = dp2[i] = mod;
    dp[n*b] = 0;
    for (int i=n-1;i>=0;i--)
    {
        int D = a[i];
        for (int j=(i+1)*b;j<=n*b;j++)
        {
            int x = dp[j], y = dp2[j];
            dp[j-b+D] = min(dp[j-b+D],x);
            dp2[j-b] = min(dp2[j-b],x+(b-D));
            dp[j-b+D+1] = min(dp[j-b+D+1],y);
            dp2[j-b] = min(dp2[j-b],y+b-(D+1));
        }
    }
    int A = mod;
    for (int i=0;i<=n*b;i++)
    {
        int x = max(i,min(dp[i],dp2[i]));
        A = min(A,x);
    }
    cout << A << "\n";

}

int main() {
//#ifdef DEBUG
//    freopen("input.txt", "r", stdin);
//#endif
    ios_base::sync_with_stdio(false);
    int t = 1;
//    cin >> t;
    for (int i = 1; i <= t; i++) {
//        cout << "Case #" << i << endl;
        solve();
    }
}