func_code_string: #include <bits/stdc++.h>   using namespace std;   long double eps = 1e-9, pi = acos(-1.0);   struct vec {     long double i, x, y;   } vectors[100005];   long double cala(const vec& v) {     long double ang = acos(v.x / sqrt(v.x * v.x + v.y * v.y));     ang = v.y > -eps ? ang : 2 * pi - ang;     return ang;   }   bool cmp(const vec& v1, const vec& v2) { return cala(v1) < cala(v2); }   int main() {     int n;     cin >> n;     for (int i = 0; i < n; i++)       cin >> vectors[i].x >> vectors[i].y, vectors[i].i = i;     sort(vectors, vectors + n, cmp);     int minp = n - 1;     long double minv =         abs((long double)2 * pi - (cala(vectors[n - 1]) - cala(vectors[0])));     for (int i = 0; i < n - 1; i++) {       if (abs(cala(vectors[i + 1]) - cala(vectors[i])) < minv)         minp = i, minv = abs(cala(vectors[i + 1]) - cala(vectors[i]));     }     if (minp == n - 1)       cout << vectors[minp].i + 1 <<     << vectors[0].i + 1 << endl;     else       cout << vectors[minp].i + 1 <<     << vectors[minp + 1].i + 1 << endl;     return 0;   }   