#include<bits/stdc++.h>
using namespace std;
#define L long long
int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    int n, m;
    cin >> n >> m;
    vector<int> nums(m,0);
    for (int i = 0; i < m; i++) {
        int v;
        cin >> v;
        nums[i] = min(v, n - v);
    }
    int best = 0;
    function<void(int,int,int,int)> solve = [&](int curr, int mask, int distinct, int remain) {
        if (curr) {
            int minV = 30;
            int minBits = 0;
            for (int j = 0; j < n; j++) {
                if ((curr>>j)&1) {
                    if (nums[j] < minV) {
                        minV = nums[j];
                        minBits = 1<<j;
                    } else if (nums[j] == minV) {
                        minBits |= 1<<j;
                    }
                }
            }
            int nex = (curr-1)&mask;
            for (int i = 0; i < minV; i++) {
                solve(nex, mask, distinct + (i == 1), remain-i);
                for (int j = 0; j < n; j++) {
                    if ((curr>>j)&1) {
                        nums[j]--;
                    }
                }
            }
            mask &= ~minBits;
            nex &= mask;
            solve(nex, mask, distinct + (minV == 1), remain-minV);
            for (int j = 0; j < n; j++) {
                if ((curr>>j)&1) {
                    nums[j] += minV;
                }
            }
        } else if (!mask) {
            best = max(best, distinct + (remain == 1));
        }
    };
    int v = (1<<m)-1;
    solve(v,v,0,n);
    cout << best << '\n';
}