#include<iostream>
#include<algorithm>;
using namespace std;
int w, n, cnt = 0;
const int maxn = 3e4;
int a[maxn];

int main()
{
	cin >> w >> n;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i];
	}
	sort(a, a + n + 1);
	int i = 1, j = n;
	while (i <= j)
	{
		cnt++;
		if (a[i] + a[j] <= w)
		{
			i++;
			j--;
		}
		else
		{
			j--;
		}
	}
	cout << cnt;
	return 0;
}