#include "bits/stdc++.h"

using namespace std;

long double start = clock();

int n, m, a[10], ans = 0, t = 0;
set<vector<int>> used[11];

void CheckTime() {
    if (t++ == 100) {
        t = 0;
        if ((long double) (clock() - start) / CLOCKS_PER_SEC > 5) {
            cout << ans;
            exit(0);
        }
    }
}

void dfs(int j, vector<int> c) {
	CheckTime();
    sort(c.begin(), c.end());
    if (j == m) {
        int cnt = 0;
        for (auto x : c) {
            cnt += x == 1;
        }
        if (ans < cnt) {
            ans = cnt;
        }
        return;
    }
    if (used[j].find(c) != used[j].end()) {
        return;
    }
    used[j].insert(c);
    vector<int> tmp;
    function<void(int, int)> gen = [&] (int i, int x) {
        if (i == (int) c.size()) {
            if (!x) {
                dfs(j + 1, tmp);
            }
            return;
        }
        for (int v = 0; v <= min(x, c[i]); v++) {
            if (v) {
                tmp.push_back(v);
            }
            if (v != c[i]) {
                tmp.push_back(c[i] - v);
            }
            gen(i + 1, x - v);
            if (v) {
                tmp.pop_back();
            }
            if (v != c[i]) {
                tmp.pop_back();
            }
        }
    };
    gen(0, a[j]);
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        cin >> a[i];
        a[i] = min(a[i], n - a[i]);
    }
    dfs(0, {n});
    cout << ans;
}