#include <bits/stdc++.h>
using namespace std;

ifstream f("grupuri.in");
ofstream g("grupuri.out");

int k, n;
int x, rez, sus;
int aux[100005];

priority_queue<int>q;

int main( )
{
    f >> k >> n;
    for (int i=1; i<=n; ++i)
    {
        f >> x;
        q.push(x);
    }
    while (1)
    {
        for (int i=1; i<=k; ++i)
        {
            sus=q.top();
            q.pop();
            if (sus==0)
            {
                g << rez;
                return 0;
            }
            sus--;
            aux[i]=sus;

        }
        for (int i=1; i<=k; ++i)
            q.push(aux[i]);
        rez++;
    }
    return 0;
}