#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	vector<pair<long long, long long>>pos(n + 1);
	rep(i, n)cin >> pos[i + 1].first >> pos[i + 1].second;
	n++;
	vector d(n, vector<double>(n));
	rep(i, n)rep(j, n) {
		double dx = pos[i].first - pos[j].first;
		double dy = pos[i].second - pos[j].second;
		d[i][j] = sqrt(dx * dx + dy * dy);
	}
	vector dp(1 << n, vector(n, vector<double>(m + 1, LINF)));
	dp[1 << 0][0][m] = 0;
	rep(i, 1 << n)rep(j, n)rep(k, m + 1) {
		if (LINF == dp[i][j][k])continue;
		rep2(nj, 1, n) {
			if (1 & (i >> nj))continue;
			int ni = i + (1 << nj);
			if (0 != k) {
				int nk = k - 1;
				auto nval = dp[i][j][k] + d[j][nj];
				chmin(dp[ni][nj][nk], nval);
			}
			{
				int nk = m - 1;
				auto nval = dp[i][j][k] + d[j][0] + d[0][nj];
				chmin(dp[ni][nj][nk], nval);
			}
		}
	}
	double ans = LINF;
	rep(j, n)rep(k, m + 1) {
		auto tmp = dp[(1 << n) - 1][j][k];
		tmp += d[j][0];
		chmin(ans, tmp);
	}
	cout << fixed << setprecision(16) << ans << endl;
	return 0;
}