N = int(input())
A = list(map(int,input().split()))

if all(a > 0 for a in A) and all(a>b for a,b in zip(A,A[1:])):
    print(-A[-1])
    exit()


INF = 10**18
p = -INF
m = 0
for a in A:
    np = max(p, m - a)
    nm = max(m, p + a)
    p,m = np,nm

print(max(p,m))