#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i=0; i<n; i++)
#define debug 0
#define YES cout << "Yes" << endl;
#define NO cout << "No" << endl;
using ll = long long;
using ld = long double;
const int mod = 998244353;
const int MOD = 1000000007;
const double pi = atan2(0, -1);
const int inf = 1 << 31 - 1;
const ll INF = 1LL << 63 - 1;
#include <time.h>
#include <chrono>

//vectorの中身を空白区切りで出力
template<typename T>
void printv(vector<T> v) {
	for (int i = 0; i < v.size(); i++) {
		cout << v[i];
		if (i < v.size() - 1) {
			cout << " ";
		}
	}
	cout << endl;
}

//vectorの中身を改行区切りで出力
template<typename T>
void print1(vector<T> v) {
	for (auto x : v) {
		cout << x << endl;
	}
}

//二次元配列を出力
template<typename T>
void printvv(vector<vector<T>> vv) {
	for (vector<T> v : vv) {
		printv(v);
	}
}

//vectorを降順にソート
template<typename T>
void rsort(vector<T>& v) {
	sort(v.begin(), v.end());
	reverse(v.begin(), v.end());
}

//昇順priority_queueを召喚
template<typename T>
struct rpriority_queue {
	priority_queue<T, vector<T>, greater<T>> pq;

	void push(T x) {
		pq.push(x);
	}

	void pop() {
		pq.pop();
	}

	T top() {
		return pq.top();
	}

	size_t size() {
		return pq.size();
	}

	bool empty() {
		return pq.empty();
	}
};

//mod mod下で逆元を算出する
//高速a^n計算(mod ver.)
ll power(ll a, ll n) {
	if (n == 0) {
		return 1;
	}
	else if (n % 2 == 0) {
		ll x = power(a, n / 2);
		x *= x;
		x %= mod;
		return x;
	}
	else {
		ll x = power(a, n - 1);
		x *= a;
		x %= mod;
		return x;
	}
}
//フェルマーの小定理を利用
ll modinv(ll p) {
	return power(p, mod - 2) % mod;
}

//Mexを求める
struct Mex {
	map<int, int> mp;
	set<int> s;
	Mex(int Max) {
		for (int i = 0; i <= Max; i++) {
			s.insert(i);
		}
	}

	int _mex = 0;
	void Input(int x) {
		mp[x]++;
		s.erase(x);
		if (_mex == x) {
			_mex = *begin(s);
		}
	}

	void Remove(int x) {
		if (mp[x] == 0) {
			cout << "Mex ERROR!: NO VALUE WILL BE REMOVED" << endl;
		}
		mp[x]--;
		if (mp[x] == 0) {
			s.insert(x);
			if (*begin(s) == x) {
				_mex = x;
			}
		}
	}

	int mex() {
		return _mex;
	}
};

//条件分岐でYes/Noを出力するタイプのやつ
void YN(bool true_or_false) {
	cout << (true_or_false ? "Yes" : "No") << endl;
}

//Union-Find
struct UnionFind {
	vector<int> par;
	UnionFind(int N) : par(N) {
		for (int i = 0; i < N; i++) {
			par[i] = -1;
		}
	}

	//root(x):xの根を求める関数
	int root(int x) {
		if (par[x] == -1) {
			return x;
		}
		else {
			return par[x] = root(par[x]);
		}
	}

	//isSame(x,y):xとyが同じグループならtrueを返す関数
	bool isSame(int x, int y) {
		if (root(x) == root(y)) {
			return true;
		}
		else {
			return false;
		}
	}

	//Union(x,y):xとyの根をつなげる関数
	void Union(int x, int y) {
		int X = root(x);
		int Y = root(y);
		if (X == Y) {
			return;
		}
		if (X < Y) {
			swap(X, Y);
		}
		par[X] = Y;
	}
};

//最大公約数(ユークリッドの互除法）
ll gcd(ll a, ll b) {
	if (b > a) {
		swap(a, b);
	}
	while (a % b != 0) {
		ll t = a;
		a = b;
		b = t % b;
	}
	return b;
}

//最小公倍数（gcdを定義しておく）
ll lcm(ll a, ll b) {
	ll g = gcd(a, b);
	ll x = (a / g) * b;
	return x;
}

struct SegTree {
	vector<int> tree;
	vector<int> lazy;
	int n = 1;
	SegTree(int N, int H) {
		while (n < N) {
			n *= 2;
		}
		vector<int> v(n * 2, H + 1);
		swap(tree, v);
		vector<int> u(n * 2, 200005);
		swap(lazy, u);
	}

	void update(int val, int l, int r, int u, int t, int now) {
		if (l >= t || r <= u) {
			return;
		}
		else if (l <= u && r >= t) {
			lazy[now] = min(lazy[now], val);
		}
		else {
			tree[now] = min(tree[now], val);
			update(val, l, r, u, (u + t) / 2, now * 2 + 1);
			update(val, l, r, (u + t) / 2, t, now * 2 + 2);
		}
	}
	void treeup(int now, int val) {
		if (tree[now] > val) {
			tree[now] = val;
			if (now > 0) {
				treeup((now - 1) / 2, val);
			}
		}
	}

	int Min(int l, int r, int u, int t, int now) {
		if (l >= t || r <= u) {
			return inf;
		}
		else if (l <= u && r >= t) {
			treeup(now, lazy[now]);
			return tree[now];
		}
		else {
			treeup(now, lazy[now]);
			lazy[now * 2 + 1] = min(lazy[now * 2 + 1], lazy[now]);
			lazy[now * 2 + 2] = min(lazy[now * 2 + 2], lazy[now]);
			return min(Min(l, r, u, (u + t) / 2, now * 2 + 1), Min(l, r, (u + t) / 2, t, now * 2 + 2));
		}
	}

	int query(int l, int r) {
		return Min(l, r, 0, n, 0);
	}
};

int N, K, m=0;
vector<vector<int>> group;
vector<vector<ld>> plot;
ld ans = INF;

ld dist(vector<ld> x, vector<ld> y) {

	ld d = sqrt((x[0] - y[0]) * (x[0] - y[0]) + (x[1] - y[1]) * (x[1] - y[1]));

	return d;
}

void calc() {
	ld score = 0;
	for (vector<int> g : group) {
		map<ll, map<int, ld>> record;
		rpriority_queue < tuple<ld, ll, int>> pq;
		record[0][0] = 0;
		pq.push({ 0,0,0 });
		while (!pq.empty()) {
			tuple<ld,ll,int> tmp = pq.top();
			pq.pop();
			ld now_score;
			bitset<15> b;
			int now;
			tie(now_score, b, now) = tmp;
			for (int x : g) {
				if (!b[x] && now != x) {
					b[x] = 1;
					ld d = dist(plot[now], plot[x]);
					if (!record[b.to_ullong()].count(x) || record[b.to_ullong()][x] > now_score + d) {
						record[b.to_ullong()][x] = now_score + d;
						pq.push({ now_score + d, b.to_ullong(), x});
					}
					b[x] = 0;
				}
			}
		}

		bitset<15> e = 0;
		for (int x : g) {
			e[x] = 1;
		}
		score += record[e.to_ullong()][0];
	}

	ans = min(ans, score);
}

void dfs(int i) {
	if (i <= N) {
		for (int j = 0; j < group.size(); j++) {
			if (group[j].size() <= K) {
				group[j].push_back(i);
				dfs(i + 1);
				group[j].pop_back();
			}
		}
		if (group.size() < m) {
			group.push_back({ 0, i });
			dfs(i + 1);
			group.pop_back();
		}
	}
	else {
		calc();
	}
}

int main() {
	cin >> N >> K;
	for (int i = 0; i < N; i += K) {
		m++;
	}
	plot.push_back({ 0,0 });
	rep(i, N) {
		ld x, y;
		cin >> x >> y;
		plot.push_back({ x,y });
	}
	dfs(1);
	cout << setprecision(10) << fixed;
	cout << ans << endl;
}