#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
#include <fstream>
#include <bitset>
   
using namespace std;
   
 
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define rforeach(it, c) for (__typeof__((c).rbegin()) it=(c).rbegin(); it != (c).rend(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define CL(arr, val) memset(arr, val, sizeof(arr))
#define COPY(dest, src) memcpy(dest, src, sizeof(dest))
#define ten(n) ((long long)(1e##n))
#define bin(n) (1LL << (n))
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define revrep(i, n) for (int i = (n); i >= 0; --i)
#define pb push_back

template <class T> void chmax(T& a, const T& b) { a = max(a, b); }
template <class T> void chmin(T& a, const T& b) { a = min(a, b); }
 
template <class T> void uniq(vector<T>& c) { sort(c.begin(), c.end()); c.erase(unique(c.begin(), c.end()), c.end()); }
 
template <class T> string to_s(const T& a) { ostringstream os; os << a; return os.str(); }
template <class T> T to_T(const string& s) { istringstream is(s); T res; is >> res; return res; }
  
template <class T, class U> ostream& operator<<(ostream& os, pair<T, U>& p) { os << "( " << p.first << ", " << p.second << " )"; return os; }
  
template <class T> void print(T a, int n, const string& deli = " ", int br = 1) { for (int i = 0; i < n; ++i) { cout << a[i]; if (i + 1 != n) cout << deli; } while (br--) cout << endl; }
template <class T> void print(const T& c, const string& deli = " ", int br = 1) { foreach (it, c) { cout << *it; if (++it != c.end()) cout << deli;--it; } while (br--) cout << endl; }
template <class T> void print2d(T a, int w, int h, int width = -1, int br = 1) { for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) {    if (width != -1) cout.width(width); cout << a[i][j] << ' '; } cout << endl; } while (br--) cout << endl; }
   
template <class T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
template <class T> void input(T* a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }

void fix_pre(int n) { cout.setf(ios::fixed, ios::floatfield); cout.precision(10); }
void fast_io() { cin.tie(0); ios::sync_with_stdio(false); }
#define trace(x) (cout << #x << ": " << (x) << endl)
 
bool in_rect(int x, int y, int w, int h) { return 0 <= x && x < w && 0 <= y && y < h; }
 

typedef long long ll;
typedef pair<int, int> pint;
 
// y(v): v>^<  y(^): ^>v<
const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };

const double PI = acos(-1.0);

#define F first
#define S second



const int M = 5 * ten(4) + 100;
const int inf = ten(8);

int w, n, x[M];
int sum_x[M];

// [i, j]
bool can_place_in_line(int i, int j)
{
    int rem_space = w - (sum_x[j + 1] - sum_x[i]);
    int num_interval = j - i;
    return num_interval > 0 && rem_space >= num_interval;
}
// [i, j]
int max_space(int i, int j)
{
    int rem_space = w - (sum_x[j + 1] - sum_x[i]);
    int num_interval = j - i;
    if (num_interval > 0 && rem_space >= num_interval)
        return (rem_space + (num_interval - 1)) / num_interval;
    else
        return inf;
}
bool can_place_in_last(int i)
{
    int rem_space = w - (sum_x[n] - sum_x[i]);
    int num_interval = n - i - 1;
    return rem_space >= num_interval;
}
bool check(int upper_space)
{
    int dp[M]; // can place i in beginning if sum_x[i=0..i](dp[i]) > 0
    fill_n(dp, n + 1, 0);
    dp[0] = 1;
    dp[1] = -1;

    int left = 0, right = 0;
    rep(i, n)
    {
        if (dp[i] > 0)
        {
            // can place [i..j](j = [left..right)) in one line
            chmax(left, i + 1);
            while (left < n && can_place_in_line(i, left) && max_space(i, left) > upper_space)
                ++left;

            chmax(right, left + 1);
            while (right < n && can_place_in_line(i, right) && max_space(i, right) <= upper_space)
                ++right;

            if (max_space(i, left) <= upper_space)
            {
                ++dp[left + 1];
                --dp[right + 1];
            }
        }

        dp[i + 1] += dp[i];
    }

    rep(i, n)
        if (dp[i] && can_place_in_last(i))
            return true;
    return false;
}
int main()
{
    while (scanf("%d%d", &w, &n), n)
    {
        rep(i, n)
            scanf("%d", x + i);

        sum_x[0] = 0;
        rep(i, n)
            sum_x[i + 1] = sum_x[i] + x[i];

        int low = 0, high = w - 2;
        while (high - low > 1)
        {
            int mid = (low + high) / 2;
            if (check(mid))
                high = mid;
            else
                low = mid;
        }
        printf("%d\n", high);
    }
}

Measured memory_bytes: 1772