#include<bits/stdc++.h>
#define f1(i, n) for(ll i=1;i<=n;++i)
#define f0(i, n) for(ll i=0;i<n;++i)
#define ull unsigned long long
#define ll long long
#define rev(a) reverse(a.begin(),a.end())
#define all(x) x.begin(),x.end()
#define so(A, n) sort(A+1, A+n+1)
using namespace std;
const int maxn = 2e5 + 1;
ll A[maxn], B[maxn];
int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int n;
	cin >> n;
	f1(i, n) {
		cin >> A[i];
	}
	int i = 1, j = 1;
	ll sum = 0, res = LLONG_MIN;
	while (j <= n) {
		if (A[j] % 3 != 0) {
			sum += A[j];
			res = max(res, sum);
			++j;
		}
		else if (A[j] % 3 == 0 || sum < 0) {
			++j;
			i = j;
			sum = 0;
		}
	}
	cout << res;

	return 0;
}