func_code_string: #include <bits/stdc++.h>   using namespace std;   mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());   mt19937 rnf(2106);   const int N = 200005, INF = 1000000009;   struct ban {     int x, y;   };   bool operator<(const ban& a, const ban& b) {     return make_pair(a.x, a.y) < make_pair(b.x, b.y);   }   double dist(const ban& a, const ban& b) {     return sqrt((a.x - b.x) * 1LL * (a.x - b.x) +                 (a.y - b.y) * 1LL * (a.y - b.y));   }   long long F(const ban& t1, const ban& t2, const ban& t) {     return (t.x - t1.x) * 1LL * (t2.y - t1.y) -            (t.y - t1.y) * 1LL * (t2.x - t1.x);   }   int n, k;   ban a[N];   bool so(int i, int j) { return a[i] < a[j]; }   bool c[N];   double solv() {     int u = -1;     for (int i = 1; i <= 3; ++i) {       for (int j = i + 1; j <= 3; ++j) {         int q = 0;         for (int k = 1; k <= n; ++k) {           if (F(a[i], a[j], a[k])) ++q;         }         if (q == 1) {           for (int k = 1; k <= n; ++k) {             if (F(a[i], a[j], a[k])) {               u = k;               break;             }           }         }       }     }     assert(u != -1);     c[u] = true;     vector<int> v;     for (int i = 1; i <= n; ++i) {       if (i == u) continue;       v.push_back(i);     }     sort((v).begin(), (v).end(), so);     double ans = INF;     if (k == u) {       for (int i = 0; i < ((int)(v).size()); ++i) {         ans =             min(ans, dist(a[k], a[v[i]]) + dist(a[v[0]], a[v.back()]) * 2 -                          max(dist(a[v[i]], a[v[0]]), dist(a[v[i]], a[v.back()])));       }     } else {       ans = min(ans, dist(a[v[0]], a[v.back()]) + dist(a[v[0]], a[k]) +                          dist(a[v.back()], a[u]));       ans = min(ans, dist(a[v[0]], a[v.back()]) + dist(a[v.back()], a[k]) +                          dist(a[v[0]], a[u]));       bool z = false;       for (int i = 0; i < ((int)(v).size()) - 1; ++i) {         if (v[i] == k) {           ans =               min(ans, dist(a[k], a[v[0]]) + dist(a[v[0]], a[u]) +                            min(dist(a[u], a[v[i + 1]]), dist(a[u], a[v.back()])) +                            dist(a[v[i + 1]], a[v.back()]));           z = true;         }         if (z)           ans = min(ans, dist(a[v[0]], a[v[i]]) + dist(a[k], a[v[0]]) +                              dist(a[v[i]], a[u]) + dist(a[u], a[v[i + 1]]) +                              dist(a[v[i + 1]], a[v.back()]));       }       reverse((v).begin(), (v).end());       z = false;       for (int i = 0; i < ((int)(v).size()) - 1; ++i) {         if (v[i] == k) {           ans =               min(ans, dist(a[k], a[v[0]]) + dist(a[v[0]], a[u]) +                            min(dist(a[u], a[v[i + 1]]), dist(a[u], a[v.back()])) +                            dist(a[v[i + 1]], a[v.back()]));           z = true;         }         if (z)           ans = min(ans, dist(a[v[0]], a[v[i]]) + dist(a[k], a[v[0]]) +                              dist(a[v[i]], a[u]) + dist(a[u], a[v[i + 1]]) +                              dist(a[v[i + 1]], a[v.back()]));       }     }     return ans;   }   double solv0() {     vector<int> v;     for (int i = 1; i <= n; ++i) {       if (i == k) continue;       v.push_back(i);     }     double ans = INF;     do {       double yans = dist(a[k], a[v[0]]);       for (int i = 0; i < ((int)(v).size()) - 1; ++i)         yans += dist(a[v[i]], a[v[i + 1]]);       ans = min(ans, yans);     } while (next_permutation((v).begin(), (v).end()));     return ans;   }   int main() {     ios_base::sync_with_stdio(false), cin.tie(0);     cout.setf(ios::fixed);     cout.setf(ios::showpoint);     cout.precision(9);     int tt = 1;     while (tt--) {       cin >> n >> k;       for (int i = 1; i <= n; ++i) cin >> a[i].x >> a[i].y;       set<pair<int, int> > s;       c[k] = true;       s.insert(make_pair(a[k].x, a[k].y));       for (int i = 1; i <= n; ++i) {         if (s.find(make_pair(a[i].x, a[i].y)) != s.end()) continue;         c[i] = true;         s.insert(make_pair(a[i].x, a[i].y));       }       vector<ban> v;       bool z = false;       for (int i = 1; i <= n; ++i) {         if (c[i]) {           c[i] = false;           v.push_back(a[i]);           if (i == k && z == false) {             z = true;             k = ((int)(v).size());           }         }       }       n = ((int)(v).size());       for (int i = 1; i <= n; ++i) a[i] = v[i - 1];       cout << solv() <<   n ;     }     return 0;   }   