N = int(input())
A = list(map(int, input().split())) 
DP = [0,-10**18]
for i,a in enumerate(A):
    NDP = [DP[1]+a if DP[1]==-10**18 else max(DP[0],DP[1]+a)   ,max(DP[1],DP[0]-a)]
    DP = NDP
print(max(DP))