import numpy as np

N, M = map(int, input().split())
A = list(map(int, input().split()))
A.sort(reverse=True)
dp = np.zeros((N + 1, M + 1), dtype=np.int64)

for i in range(N - 1):
    dp[i + 2] = dp[i + 1]
    diff = A[i] - A[i + 1]
    if diff > M:
        continue
    dp[i + 2, diff:] = np.maximum(dp[i, : M + 1 - diff] + A[i], dp[i + 2, diff:])

print(dp[N].max())