#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int main()
{
	freopen("group.in","r",stdin);
	freopen("group.out","w",stdout);
	int m;
	cin>>m;
	int n;
	cin>>n;
	int a[n+1];
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	int cnt=0;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(a[i]>a[j]) 
			{
				int t=a[i];
				a[i]=a[j];
				a[j]=t;
			}
		}
	}
	bool b[n+1];
	memset(b,false,sizeof(b));
	for(int i=1;i<=n;i++)
	{
		int j=n;
		while((!b[j]||(b[i]+b[j])>m)&&j>i)
		{
			j--;
		}
		if(b[j]&&(b[i]+b[j])<=m)
		{
			b[j]=true;
			b[i]=true;
			cnt++;	
		}
		else if(!b[i])
		{
			b[i]=true;
			cnt++;
		}
	}
	cout<<cnt<<endl;
	return 0;
}