```
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
int a[30001];
bool b[30001];
int main()
{
int m,n,ans=0;
cin>>m>>n;
for(int i=1;i<=n;i++)
cin>>a[i];
sort(a+1,a+n+1);
int head=1,tail=n;
while(head<tail){
if(a[head]+a[tail]<=m)
head++,tail--,ans++;
else
tail--,ans++;
if(head==tail)
ans++;
}
cout<<ans;
return 0;
}
```
by Clearlove7loveyou @ 2019-01-05 11:35:52