#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;

int w,n,pr[205];
int p,tot;

int main()
{
	cin>>w>>n;
	for(int i=0;i<n;i++)
	{
		cin>>p;
		pr[p]++;
	}
	int count=0;
	count+=pr[w];
	tot+=pr[w];
	for(int i=5;i<=w/2;i++)
	{
		if(pr[i]>0)
		{
			for(int j=w-i;j>=5;j--)
			{
				while(pr[j]>0&&pr[i]>0&&!(i==j&&pr[i]==1))
				{
					count++;//cout<<i<<" "<<j<<endl;
					pr[j]--;pr[i]--;
					tot+=2;
				}
				if(pr[i]==0)break;
			}
		}
	}//cout<<"tot="<<tot<<endl;cout<<"count="<<count<<endl;
	int ok=0;
	for(int i=(w+1)/2;i>=5;i--)
	{
		if(pr[i]!=0)
		{//cout<<i<<endl;
			ok++;break;
		}
	}
	if(ok==1)count++;
	else count+=n-tot;
	cout<<count;
	return 0;
}