N=int(input())
A=list(map(int,input().split()))
dp=[[-float("inf"),-float("inf")]for _ in range(N)]
dp[0][1]=-A[0]
dp[1][1]=-(min(A[0],A[1]))
for i in range(2,N):
    for j in range(2):
        dp[i][j]=max(dp[i-1][j],dp[i-1][j^1]+A[i]*(-1)**j)
print(max(dp[-1]))