func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     unsigned long long n, ans = 0, a[30], cur, deg = 20, countOfPair = 1;     cin >> n;     memset(a, 0, sizeof(unsigned long long) * 30);     for (int i = 0; i < n; ++i) {       cin >> cur;       ++a[cur + 10];     }     for (int i = 0; i < 10; ++i) {       ans += a[i] * a[deg + i];       deg -= 2;     }     if (a[10] != 0 && a[10] != 1) {       if (a[10] == 2)         ans += 1;       else {         for (unsigned int i = 3; i <= a[10]; ++i) {           countOfPair = countOfPair + i - 1;         }         ans += countOfPair;       }     }     cout << ans;     cin >> n;     return 0;   }   