N = int(input())

ax = list(map(int, input().split()))

mm = 0

while len(ax) != 0:
    left = ax[0] - ax[1]
    right = ax[-1] - ax[-2]

    if left > right:
        mm += left
        ax.pop(0)
        ax.pop(0)
    else:
        mm += right
        ax.pop()
        ax.pop()

print(mm)