#include <fstream>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <climits>

#include <ctype.h>

#define MAX 100000000


using namespace std;


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

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

int n,k,v[1000005],sol=0;

int main(){

    f>>k>>n;

    for(int i=1;i<=n;i++){
        f>>v[i];
    }
    sort(v+1,v+n+1);

    while(v[n-k+1] > 0){
        sol+=1;

        for(int i=n;i>=n-k+1;i--){
            v[i]--;
        }

        sort(v+1,v+n+1);
    }

    g<<sol;


    f.close();
    g.close();
    return 0;
}