func_code_string: #include <bits/stdc++.h>   using namespace std;   long long a[100005], n, s, ans;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     cin >> n;     while (n--) {       long long x;       cin >> x;       s += x;       a[x]++;     }     if (s == 1 or s == 2 or s == 5) return cout << -1, 0;     while (a[1] > 0 and a[2] > 0) {       a[3]++;       ans++;       a[1]--;       a[2]--;     }     if (a[1] > 0) {       ans += a[1] - a[1] / 3;       if (a[1] == 1 and a[3] == 0) ans++;     }     if (a[2] > 0) {       ans += a[2] - a[2] / 3;       if (a[2] % 3 == 1 and a[4] == 0) ans++;     }     cout << ans;     return 0;   }   