func_code_string: #include <bits/stdc++.h>   using namespace std;   const long double pi = acos(-1.0L);   signed main() {     long long n;     cin >> n;     long double x[n], y[n];     for (long long i = (0); i < (n); ++i) cin >> x[i] >> y[i];     long long ans = 0;     for (long long i = (0); i < (n); ++i) {       vector<long double> v;       for (long long j = (0); j < (n); ++j)         if (j != i) {           v.push_back(atan2(y[j] - y[i], x[j] - x[i]));         }       sort(v.begin(), v.end());       long long f[n - 1], s[n - 1];       long long k = 0;       for (long long j = (0); j < (n - 1); ++j) {         while (k < n - 1 && v[k] < v[j] + pi) ++k;         f[j] = k;         s[j] = (j ? s[j - 1] : 0) + f[j];       }       for (long long j = (0); j < (n - 1); ++j) {         ans += (s[f[j] - 1] - s[j]) - (f[j]) * (f[j] - j - 1);       }     }     cout << ans * (n - 4) / 2 << endl;   }   