#include<bits/stdc++.h>
using namespace std;

int n,w,a[31086],num;

int main () {
    
    freopen("kaj.in","r",stdin);
    freopen("kaj.out","w",stdout);
    
    cin>>w>>n;
    int tp=n;
    for(int i = 0; i<n; i++){
        cin>>a[i];
    }
    
    sort(a,a+n);
    int l=0,r=n-1;
    cout<<endl;
    while(tp>=1){
        int u=0;
        while(a[l]+a[r]<=w){
            l++;
            if(l>=r){
                l=n-tp;
                break;
            }
        }
        if(l>0)l--;
        if(a[l]+a[r]<=w){
            tp--;
            l++;
        }
        
        r--;
        tp--;
        num++;
    }
    
    cout<<num;
    
    return 0;
}