func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   using minpq = priority_queue<T, vector<T>, greater<T>>;   struct pt {     long long x, y;     pt(long long x = 0, long long y = 0) : x(x), y(y) {}     pt operator-(const pt &o) const { return pt(x - o.x, y - o.y); }     long long cross(const pt &o) const { return x * o.y - y * o.x; }   };   struct city {     pt p;     bool b;     int id;   };   struct tri {     city a, b, c;     bool ins(const pt &p) {       return (b.p - a.p).cross(p - a.p) > 0 && (c.p - b.p).cross(p - b.p) > 0 &&              (a.p - c.p).cross(p - c.p) > 0;     }   };   const int N = 1e3 + 5;   int n;   vector<city> v;   bool used[N];   vector<city> upperhull(const vector<city> &v, int n) {     vector<city> u;     for (int m, i = 0; i < n; i++) {       while ((m = u.size()) > 1) {         pt p = u[m - 1].p, q = u[m - 2].p;         if ((p - q).cross(v[i].p - p) > 0) break;         u.pop_back();       }       u.push_back(v[i]);     }     return u;   }   vector<city> hull(vector<city> &v, int n) {     vector<city> u = upperhull(v, n);     reverse(v.begin(), v.end());     vector<city> l = upperhull(v, n);     reverse(v.begin(), v.end());     for (int i = 1; i + 1 < l.size(); i++) u.push_back(l[i]);     return u;   }   vector<pair<int, int>> ans;   void solve(tri T, vector<city> v) {     v.erase(remove_if((v).begin(), (v).end(),                       [&](city c) { return used[c.id] || !T.ins(c.p); }),             v.end());     int cnt[2] = {0, 0};     for (city c : {T.a, T.b, T.c}) {       cnt[c.b]++;     }     bool b = (cnt[0] > cnt[1]);     for (city &c : v) {       if (c.b == b) {         for (city d : {T.a, T.b, T.c}) {           if (c.b == d.b) {             ans.emplace_back(c.id, d.id);             break;           }         }         used[c.id] = true;         solve({T.a, T.b, c}, v);         solve({T.b, T.c, c}, v);         solve({T.c, T.a, c}, v);         return;       }     }     city c1 = (T.a.b != b ? T.a : T.b.b != b ? T.b : T.c);     for (city &c : v) {       ans.emplace_back(c.id, c1.id);     }   }   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cin >> n;     for (int i = (0); i < (n); i++) {       pt p;       bool b;       cin >> p.x >> p.y >> b;       v.push_back({p, b, i});     }     if (n == 1 || (n == 2 && v[0].b != v[1].b)) {       cout <<  0 n ;       return 0;     } else if (n == 2) {       cout <<  1 n0 1 n ;       return 0;     }     sort((v).begin(), (v).end(), [&](city &a, city &b) {       return make_pair(a.p.x, a.p.y) < make_pair(b.p.x, b.p.y);     });     vector<city> h = hull(v, n);     vector<int> ve;     for (int i = (0); i < (((int)(h).size())); i++) {       if (h[i].b != h[(i + 1) % ((int)(h).size())].b) {         ve.push_back(i);       } else {         ans.emplace_back(h[i].id, h[(i + 1) % ((int)(h).size())].id);       }     }     if (((int)(ve).size()) > 2) {       cout <<  Impossible n ;       return 0;     }     vector<tri> tris;     for (city &c : h) {       used[c.id] = true;     }     if (ve.empty()) {       ans.pop_back();       bool flag = false;       for (city &c : v) {         if (!used[c.id] && c.b != h[0].b) {           used[c.id] = true;           for (int i = (0); i < (((int)(h).size())); i++) {             tris.push_back({h[i], h[(i + 1) % ((int)(h).size())], c});           }           flag = true;           break;         }       }       if (!flag) {         cout << n - 1 <<   n ;         for (int i = (1); i < (n); i++) {           cout << 0 <<     << i <<   n ;         }         return 0;       }     } else {       assert(((int)(ve).size()) == 2);       for (int i = (ve[0] + 1) % ((int)(h).size()); i != ve[1];            i = (i + 1) % ((int)(h).size())) {         tris.push_back({h[ve[0]], h[i], h[(i + 1) % ((int)(h).size())]});       }       for (int i = (ve[1] + 1) % ((int)(h).size()); i != ve[0];            i = (i + 1) % ((int)(h).size())) {         tris.push_back({h[ve[1]], h[i], h[(i + 1) % ((int)(h).size())]});       }     }     for (tri &T : tris) {       solve(T, v);     }     cout << ((int)(ans).size()) <<   n ;     for (pair<int, int> &pa : ans) {       cout << pa.first <<     << pa.second <<   n ;     }   }   