func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     int n, v;     int sum = 0;     int cnt[10];     memset(cnt, 0, sizeof cnt);     cin >> n;     while (n--) {       cin >> v;       cnt[v]++;       sum += v;     }     if (cnt[0] == 0) {       cout <<  -1 ;       return 0;     }     int mod = sum % 3;     if (mod != 0) {       bool deleted = 0;       for (int i = mod; i < 9; i += 3) {         if (cnt[i] > 0) {           deleted = 1;           cnt[i]--;           break;         }       }       if (!deleted) {         int left = 2;         for (int i = mod == 1 ? 2 : 1; i < 9 && left; i += 3) {           int take = min(left, cnt[i]);           left -= take;           cnt[i] -= take;         }       }     }     string res;     for (int i = 9; i >= 0; i--) {       if (i == 0 && res.empty()) cnt[0] = 1;       res += string(cnt[i],  0  + i);     }     cout << res;   }   