#include <bits/stdc++.h>
using namespace std;
const int INF = 1000000000;
int main(){
  int N, M;
  cin >> N >> M;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  sort(A.begin(), A.end(), greater<int>());
  vector<vector<int>> dp(N + 1, vector<int>(M + 1, -INF));
  dp[0][0] = 0;
  for (int i = 0; i < N; i++){
    for (int j = 0; j <= M; j++){
      if (dp[i][j] >= 0){
        dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
        if (i < N - 1){
          int d = A[i] - A[i + 1];
          if (j + d <= M){
            dp[i + 2][j + d] = max(dp[i + 2][j + d], dp[i][j] + A[i]);
          }
        }
      }
    }
  }
  int ans = 0;
  for (int i = 0; i <= M; i++){
    ans = max(ans, dp[N][i]);
  }
  cout << ans << endl;
}