func_code_string: #include <bits/stdc++.h>   using namespace std;   const double pi = 2.0 * acos(0.0);   const double eps = 1.0e-9;   const int dr[] = {-1, 0, 1, 0}, dc[] = {0, 1, 0, -1};   const int dr6[] = {1, 1, 0, -1, -1, 0}, dc6[] = {0, 1, 1, 0, -1, -1};   const int dr8[] = {-1, -1, 0, 1, 1, 1, 0, -1},             dc8[] = {0, 1, 1, 1, 0, -1, -1, -1};   int main(void) {     int kase = 1000000000;     for (int ks = 1, n; ks <= kase && cin >> n; ++ks) {       int c[32] = {0};       for (int i = 0, x; i < n && cin >> x; ++i) ++c[x + 16];       long long s = (long long)c[16] * (c[16] - 1) / 2;       for (int i = 1; i <= 10; ++i) s += (long long)c[16 - i] * c[16 + i];       cout << s << endl;     }     return 0;   }   