def tenhom(N, A):
    p = 0
    for i in range(N):
        left = A[0] - A[1]
        right = A[-1] - A[-2]
        if left > right:
            p += left
            A.pop(0)
            A.pop(0)
        elif right > left:
            p += right
            A.pop(-1)
            A.pop(-1)
        elif left == right:
            N2 = len(A) // 2 - 1
            Al = [] + A
            Ar = [] + A
            Al.pop(0)
            Al.pop(0)
            Ar.pop(-1)
            Ar.pop(-1)
            pl = left + tenhom(N2, Al)
            pr = right + tenhom(N2, Ar)
            if pl >= pr:
                p += pl
                break
            else:
                p += pr
                break
    return p

def main():
    N = int(input())
    A = list(map(int, input().split()))
    print(tenhom(N, A))

if __name__ == '__main__':
    main()