int input INF -float inf INF INF ans for in range int input if max els

n = int(input())
INF = -float('inf')
a = [INF]*3
b = [INF]*3
ans = 0
for i in range(n):
    x = int(input())
    if x > 0: a[x%3] = max(a[x%3],x)
    else:
        ans = max(ans,a[0]+b[0],a[1]+b[2],a[2]+b[1])
        for j in range(3):
            b[j] = max(b[j],a[j])
            a[j] = INF
ans = max(ans,a[0]+b[0],a[1]+b[2],a[2]+b[1])
print(ans)