N=int(input())
A=list(map(int,input().split()))
count = 0
while len(A)>=2:
    if max(A[0]-A[1],A[-1]-A[-2])==A[0]-A[1]:
        count += A[0]-A[1]
        A=A[2:]
    else:
        count+=A[-1]-A[-2]
        A=A[:-2]
print(count)