#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define pb push_back
#define SZ(a) ((int)a.size())
#define ALL(v) v.begin(), v.end()

set<vector<int>> dp, ndp, done;

void get_dp(int n, int a) {
    //cerr << "get_dp " << a << "\n";
    auto relax = [&](vector<int> mask) {
        /*cerr << "insert ";
        for (int p : mask)
            cerr << p << " ";
        cerr << endl;*/
        sort(ALL(mask));
        ndp.insert(mask);
    };

    for (auto cur : dp) {
        if (done.find(cur) != done.end()) continue;
        done.insert(cur);
        vector<int> nset;
        reverse(ALL(cur));
        auto _dfs = [&](auto dfs, int u, int one, int sum, pii lst) {
            if (u == SZ(cur)) {
                if (one <= sum) 
                    relax(nset);
                return;
            }
            for (int i = max({0, one - (sum - cur[u]), (lst.X == cur[u] ? lst.Y : 0)}); i <= one && i <= cur[u]; ++i) {
                int osz = SZ(nset);
                if (i > 1)
                    nset.pb(i);
                if (cur[u] - i > 1)
                    nset.pb(cur[u] - i);
                dfs(dfs, u + 1, one - i, sum - cur[u], pii(cur[u], i));
                nset.resize(osz);
            }
        };
        _dfs(_dfs, 0, a, n, pii(-1, -1));
    }
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int n, m;
    cin >> n >> m;
    dp.insert({n});
    while (m--) {
        int a;
        cin >> a;
        ndp.clear();
        get_dp(n, min(a, n - a));
        dp.swap(ndp);
        if (dp.find({}) != dp.end()) break;
    }
    int ans = 0;
    for (auto p : dp) {
        int sum = 0;
        for (int q : p)
            sum += q;
        ans = max(ans, n - sum);
    }
    for (auto p : done) {
        int sum = 0;
        for (int q : p)
            sum += q;
        ans = max(ans, n - sum);
    }
    cout << ans << "\n";
}