func_code_string: #include <bits/stdc++.h>   using namespace std;   const int OO = (int)2e9;   const double PI = 2 * acos(0.0);   const double EPS = 1e-9;   int dcmp(double a, double b) { return fabs(a - b) <= EPS ? 0 : a > b ? 1 : 2; }   int DI[] = {-1, 0, 1, 0, 1, -1, -1, 1};   int DJ[] = {0, 1, 0, -1, 1, -1, 1, -1};   map<int, long long> m;   int main() {     int n;     cin >> n;     for (int i = 0; i < (int)n; i++) {       int x;       cin >> x;       m[x]++;     }     long long ans = 0;     for (int i = -10; i < 0; i++)       if (m.count(i) && m.count(abs(i))) ans += (m[i] * m[abs(i)]);     if (m.count(0)) {       for (long long t = m[0] - 1; t > 0; t--) ans += t;     }     cout << ans << endl;     return 0;   }   