n, p = map(int, input().split())
h_ls = [int(h) for h in input().split()]

memo = [[0, p] for i in range(n)]
for i in range(1, n):
    c0 = memo[i - 1][0]
    c1 = memo[i - 1][1]
    cost_0 = max(h_ls[i] - h_ls[i - 1], 0)
    cost_1 = max(h_ls[i - 1] - h_ls[i], 0)
    
    memo[i][0] = min(c0 + cost_0, c0 + p, c1 + p)
    memo[i][1] = min(c1 + cost_1, c1 + p, c0 + p)

print(min(memo[-1]))