#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin ("grupuri.in");
ofstream fout ("grupuri.out");
int k,n,i,nr,v[100001];
int main()
{
    fin>>k>>n;
    for (i=1; i<=n; i++)
        fin>>v[i];
    for (; ;)
    {
        for (i=n; i>=n-k+1; i--)
        {
            if (v[i]==0)
            {
                fout<<nr;
                return 0;
            }
            v[i]--;
        }
        nr++;
        sort (v+1,v+n+1);
    }
    return 0;
}