func_code_string: #include <bits/stdc++.h>   using namespace std;   void hehe() {     int n;     cin >> n;     vector<int> arr(n);     for (int i = 0; i < n; i++) {       cin >> arr[i];     }     sort(arr.rbegin(), arr.rend());     vector<long long int> rem;     for (int i = 0; i < n - 1; i++) {       if (arr[i] - arr[i + 1] < 2) {         i++;         rem.push_back(arr[i]);       }     }     long long int ans = 0;     for (int i = 0; i + 1 < rem.size(); i += 2) {       ans += (long long int)(rem[i] * rem[i + 1]);     }     cout << ans;   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     int t = 1;     while (t--) {       hehe();     }     return 0;   }   