ソースコード
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define FOR(i, s, e) for (ll(i) = (s); (i) < (e); (i)++)
#define FORR(i, s, e) for (ll(i) = (s); (i) > (e); (i)--)
#define debug(x) cout << #x << ": " << x << endl
#define mp make_pair
#define pb push_back
const ll MOD = 1000000007;
const int INF = 1e9;
const ll LINF = 1e16;
const double PI = acos(-1.0);
int dx[8] = { 0, 0, 1, -1, 1, 1, -1, -1 };
int dy[8] = { 1, -1, 0, 0, 1, -1, 1, -1 };
/* ----- xtimex Problem: __CONTEST_NAME__ / Link: ----- */
/* ------問題------
-----問題ここまで----- */
/* -----解説等-----
----解説ここまで---- */
ll N;
int a[100005];
ll ans = 0LL;
int main() {
cin.tie(0);
ios_base::sync_with_stdio(false);
vector<int>v[3];
ll sum = 0;
cin >> N;
FOR(i, 0, N) {
cin >> a[i];
v[a[i] % 3].push_back(a[i]);
sum += a[i];
}
FOR(i, 0, 3)
sort(v[i].begin(), v[i].end());
if (sum % 3 == 0) {
cout << sum << endl;
return 0;
}
else if (sum % 3 == 1) {
int s = INF;
int t = INF;
if (v[1].size() >= 1) {
s = v[1][0];
}
if (v[2].size() >= 2) {
t = v[2][0] + v[2][1];
}
if (s != INF or t != INF) {
ans = max(sum - t, sum - s);
if (ans != 0) {
cout << ans << endl;
return 0;
}
}
}
else {
int s = INF;
int t = INF;
if (v[2].size() >= 1) {
s = v[2][0];
}
if (v[1].size() >= 2) {
t = v[1][0] + v[1][1];
}
if (s != INF or t != INF) {
ans = max(sum - t, sum - s);
if (ans != 0) {
cout << ans << endl;
return 0;
}
}
}
cout << -1 << endl;
return 0;
}