c++

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

int w, n;
int P[30005];

int main() {
    cin >> w >> n;
    for (int i = 0; i < n; i++) {
        cin >> P[i];
    }

    sort(P, P + n);

    int left = 0, right = n - 1;
    int groups = 0;

    while (left <= right) {
        if (P[left] + P[right] <= w) {
            // 可以配对
            left++;
            right--;
            groups++;
        } else {
            // 不可配对，大的单独一组
            right--;
            groups++;
        }
    }

    cout << groups << endl;

    return 0;
}