题解

沙发！

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

typedef long long ll;
typedef long double ld;

#define mpa make_pair
#define pb push_back
#define ins insert
#define f first
#define s second
#define all(x) x.begin(), x.end()
#define nl "\n"


int MOD = 1;

bool cmp(int &a, int &b) {
	return (a % MOD) > (b % MOD);
}

void solve() {
	int N, K;
	cin >> N >> K;
	vector<int> A(N);
	int maxD = 0;
	for (int i = 0; i < N; i++) {
		cin >> A[i];
		maxD = max(maxD, A[i]);
	}
	int mx = 0;
	for (int i = 1; i <= maxD; i++) {
		int amount = 0;
		for (int j = 0; j < N; j++) { amount += A[j] / i; }
		if (amount < K / 2) { continue; }
		if (amount >= K) {
			mx = max(mx, (K / 2) * i);
			continue;
		}
		MOD = i;
		sort(all(A), cmp);
		int cur = (amount - K / 2) * i;
		for (int j = 0; j < N && j + amount < K; j++) { cur += A[j] % i; }
		mx = max(mx, cur);
	}
	cout << mx << nl;
}

int main() {
    cout.sync_with_stdio(false);
    cout.tie(0);
	solve();
}