#include<bits/stdc++.h>
using namespace std;
int main() {
    int n, m,a[10001];
    cin >> m >> n;
    for (int i = 1; i <= n; i++) {
    	cin>>a[i];
    }
    sort(a+1,a+n+1);
    int b=1,s=0;
    for(int i=n;i>=b;i--){
		for(int j=b;j<=i;j++){
			if(a[i]+a[j]>=m){
				s++;
				break;
			}else if(a[i]+a[j]<=m){
				b++;
				s++;
				break;
			}
		}
	}
	cout<<s;
    return 0;
}