B. Merge it!
#include <iostream>
#include <cstdio>
using namespace std;
int n, a, ct[5], ans;
int main() {
int t;
cin >> t;
while (t--) {
memset(ct, 0, sizeof(ct));
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a;
ct[a%3]++;
}
ans = ct[0];
int x = min(ct[1], ct[2]);
ans += x;
ct[1]-=x;
ct[2]-=x;
ans += (ct[1]/3) + (ct[2]/3);
cout << ans << "\n";
}
}