n, p = map(int, input().split())
h = list(map(int, input().split()))

up = []
for i in range(n-1):
    diff = h[i+1] - h[i]
    up.append(max(0, diff))

total_up = sum(up)

max_gain = 0
current_sum = 0

for u in up:
    current_sum += u
    candidate = current_sum - p
    if candidate > 0:
        if candidate > max_gain:
            max_gain = candidate
    else:
        current_sum = 0  # Reset if this segment isn't beneficial

print(total_up - max_gain)