Untitled

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

typedef long long LL;
typedef vector<int> vi;

int main()
{
    int chargers, sockets;
    cin >> chargers >> sockets;
    vi a(chargers);
    for (int i = 0; i < chargers; ++i) {
        cin >> a[i];
    }
    if (chargers == 1 || sockets == 1) {
        cout << 1 << '\n';
        return 0;
    }
    int l = 1, r = chargers + 1;
    sort(a.begin(), a.end());
    while (l + 1 < r) {
        int m = (l + r) / 2;
        vi cnt(3);
        LL x = 0;
        for(int i = 0; i < m-2; i++){
            x += a[i] / 3;
            cnt[a[i] % 3]++;
        }
        int k = min(cnt[1], cnt[2]);
        x += k;
        x += (cnt[1] - k + 1) / 2;
        x += cnt[2] - k;
        if (x <= sockets - 2)
            l = m;
        else
            r = m;
    }
    cout << l << '\n';

    return 0;
}