#include<bits/stdc++.h>
using namespace std;
const int N = 2e6 + 10;
int w,n,a[N];
int main()
{
cin >> w >> n;
for(int i = 1;i <= n;i ++){
cin >> a[i];
}
sort(a + 1, a + 1 + n);
int sum = 0;
int j = n;
for(int i = 1;i <= j - 1;i ++){
while(j > i && a[j] + a[i] > w){
j --;
sum ++;
}
if(a[i] + a[j] <= w){
sum ++;
j --;
}
if(i + 1 == j) sum ++;
}
cout << sum;
return 0;
}
