Omenat

/*
	DONE, NEXT
*/


#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;

int main() {
	int n;
	cin >> n;

	unsigned int painot[n];
	unsigned long summa=0;
	bool isModOne = false;
	bool isModTwo = false;
	for (int i = 0; i < n; ++i) {
		cin >> painot[i];
		summa += painot[i];
		if (painot[i]%3==1) {
			isModOne=true;
		}
		if (painot[i]%3==2) {
			isModTwo=true;
		}
	}

	if (summa<3) {
		cout << 0 << endl;
		return 0;
	}

	unsigned int delta = summa%3;

	if (delta==0) {
		cout << n << endl;
		return 0;
	}

	if ((isModOne && delta==1) || (isModTwo && delta==2))  {
		cout << n-1 << endl;
		return 0;
	}
	if (n==0) {
		cout << 0 << endl;
		return 0;
	}
	if (n==1) {
		cout << (painot[1]%3==0) << endl;
		return 0;
	}

	cout << n-2 << endl;

	return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 1

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED

Test 17

Group: 3

Verdict: ACCEPTED

Test 18

Group: 3

Verdict: ACCEPTED