import sys
input = sys.stdin.readline
N = int(input())
A = list(map(int, input().split()))
INF = 10**18
dp = [[[-INF for _ in range(2)] for _ in range(2)] for _ in range(N+1)]
dp[0][0][0] = 0
for i in range(N):
    for j in range(2):
        for k in range(2):
            if dp[i][j][k]==-INF:
                continue
            dp[i+1][j][k] = max(dp[i+1][j][k], dp[i][j][k])
            dp[i+1][1-j][1] = max(dp[i+1][1-j][1], dp[i][j][k] + A[i]*(-1 if j%2==0 else 1))
ans = -INF
for j in range(2):
    ans = max(ans, dp[N][j][1])
print(ans)