#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
long long dp[3003][3003];
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	vector<int>a(n);
	rep(i, n)cin >> a[i];
	sort(allR(a));
	rep(i, 3001)rep(j, 3001)dp[i][j] = -LINF;
	dp[0][0] = 0;
	rep(i, n) {
		rep(j, m + 1) {
			//配るdp
			if (-LINF == dp[i][j])continue;
			//取らない
			chmax(dp[i + 1][j], dp[i][j]);
			//取る
			if ((m >= j + (a[i] - a[i + 1])) && (i < n - 1)) {
				chmax(dp[i + 2][j + (a[i] - a[i + 1])], dp[i][j] + a[i]);
			}
		}
	}
	long long ans = -LINF;
	rep(i, m + 1)chmax(ans, dp[n][i]);
	cout << ans << endl;
	return 0;
}