#include <vector>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("grupuri.in");
ofstream cout("grupuri.out");
int main() {
	int AnimalePerGrup, NrDeGrupuri=0,n;
	cin >> AnimalePerGrup>> n;
	vector<int>SirDeAnimale(n);
	for (int i = 0; i < n; i++) {
		cin >> SirDeAnimale[i];
	}
	sort(SirDeAnimale.begin(), SirDeAnimale.end(),greater<int>());
	int NrDeZerouri = count(SirDeAnimale.begin(), SirDeAnimale.end(), 0);
	while (NrDeZerouri <= n - AnimalePerGrup) {
		for (int i = 0; i<AnimalePerGrup; i++) {
			if (i + 1 << SirDeAnimale.size() > n-1) {
				while (SirDeAnimale[i] < SirDeAnimale[i + 1]) {
					i++;
					if (i + 1 > n-1) {
						break;
					}
				}
			}
			SirDeAnimale[i]--;
			if (SirDeAnimale[i] == 0) {
					NrDeZerouri++;
			}
		}
		NrDeGrupuri++;
	}
	cout << NrDeGrupuri;
}