func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       int n;       cin >> n;       vector<int> a(n);       for (int i = 0; i < n; i++) cin >> a[i];       for (int i = 0; i < n - 1; i += 2) {         cout << a[i + 1] <<     << -1 * a[i] <<    ;       }       cout << endl;     }     return 0;   }   