#include <bits/stdc++.h>   using namespace std;   const int OO = (int)1e9 + 1;   const int MAX = 1e5 + 1;   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int n, x, arr[3] = {};     cin >> n;     for (int i = 0; i < n; i++) {       cin >> x;       arr[x]++;     }     if (!arr[1])       cout << 0 << endl;     else if (arr[1] > arr[2])       cout << arr[2] + (arr[1] - arr[2]) / 3 << endl;     else if (arr[2] >= arr[1])       cout << arr[1] << endl;   }   