题解

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

int main()
{
int a[30009], m, n, c = 0, i, l = 1, r;
cin >> m;
cin >> n;
r = n;
for(i = 1; i <= n; i++)
{
cin >> a[i];
}
sort(a + 1, a + n + 1);
while(l <= r)
{
if(a[l] + a[r] <= m)
{
l++;
r--;
c++;
}
else
{
r--;
c++;
}
}
cout << c;
return 0;
}