#include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     long long int t;     t = 1;     while (t--) {       long long int n, c1 = 0, c2 = 0, x;       cin >> n;       while (n--) {         cin >> x;         if (x == 1)           c1++;         else           c2++;       }       x = min(c1, c2);       c1 -= x;       c2 -= x;       cout << x + (c1 / 3);     }     return 0;   }   