#include<bits/stdc++.h>
#include<atcoder/all>
namespace my{
using namespace std;
#define eb emplace_back
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define VV(n,...) vec<ll>__VA_ARGS__;setsize({n},__VA_ARGS__);vin(__VA_ARGS__)
#define FO(n) for(ll ij=n;ij--;)
#define FOR(i,...) for(auto[i,i##stop,i##step]=range(0,__VA_ARGS__);i<i##stop;i+=i##step)
#define fo(i,...) FO##__VA_OPT__(R)(i __VA_OPT__(,__VA_ARGS__))
#define fe(a,i,...) for(auto&&__VA_OPT__([)i __VA_OPT__(,__VA_ARGS__]):a)
#define single_testcase void solve();}int main(){my::io();my::solve();}namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ld=long double;
using ll=long long;
template<class...A>auto range(bool s,A...a){array<ll,3>r{0,0,1};ll I=0;((r[I++]=a),...);if(!s&&I==1)swap(r[0],r[1]);r[0]-=s;return r;}
constexpr char nl=10;
constexpr char sp=32;
constexpr auto square(auto x){return x*x;}
constexpr ll pw2(ll n){return 1LL<<n;}
constexpr ll at2(auto x,ll i){return x>>i&1;}
bool amin(auto&a,const auto&b){return a>b?a=b,1:0;}

template<class V>concept vectorial=is_base_of_v<vector<typename V::value_type>,V>;
template<class T>struct vec_info{using core_type=T;static constexpr int dim=0;};
template<vectorial V>struct vec_info<V>{using core_type=typename vec_info<typename V::value_type>::core_type;static constexpr int dim=vec_info<typename V::value_type>::dim+1;};
template<class T>using core_t=vec_info<T>::core_type;
template<class V>istream&operator>>(istream&i,vector<V>&v){fe(v,e)i>>e;return i;}
template<class V>ostream&operator<<(ostream&o,const vector<V>&v){fe(v,e)o<<e<<string(&e!=&v.back(),vectorial<V>?nl:sp);return o;}

template<class V>struct vec:vector<V>{
  using vector<V>::vector;
  vec(const vector<V>&v){vector<V>::operator=(v);}

  vec&operator^=(const vec&u){this->insert(this->end(),u.begin(),u.end());return*this;}
  vec operator^(const vec&u)const{return vec{*this}^=u;}
  vec&operator++(){fe(*this,e)++e;return*this;}
  vec&operator--(){fe(*this,e)--e;return*this;}
};
template<class T=ll,size_t n,size_t i=0>auto make_vec(const ll(&s)[n],T x={}){if constexpr(n==i+1)return vec<T>(s[i],x);else{auto X=make_vec<T,n,i+1>(s,x);return vec<decltype(X)>(s[i],X);}}
template<ll n,class...A>void setsize(const ll(&l)[n],A&...a){((a= make_vec(l,core_t<A>())),...);}

template<bool is_negative=false>struct infinity{
  template<integral T>constexpr operator T()const{return numeric_limits<T>::max()*(1-is_negative*2);}
  template<floating_point T>constexpr operator T()const{return static_cast<ll>(*this);}
  template<class T>constexpr bool operator==(T x)const{return static_cast<T>(*this)==x;}
  constexpr auto operator-()const{return infinity<!is_negative>();}
};
constexpr infinity oo;

void lin(auto&...a){(cin>>...>>a);}
void vin(auto&...a){fo(i,(a.size()&...))(cin>>...>>a[i]);}
template<char c=sp>void pp(const auto&...a){ll n=sizeof...(a);((cout<<a<<string(--n>0,c)),...);cout<<nl;}

single_testcase
void solve(){
  LL(N,K);
  VV(N,x,y);
  x.eb(0);
  y.eb(0);

  auto dist=[&](ll i,ll j)->ld{
    return sqrtl(square(x[i]-x[j])+square(y[i]-y[j]));
  };

  auto mem=make_vec({pw2(N),K+1,N+1},ld{-1});
  auto f=[&](auto&f,ll S,ll k,ll i){
    if(mem[S][k][i]!=-1)return mem[S][k][i];
    if(S==pw2(N)-1)return dist(i,N);

    ld res=oo;
    if(k)fo(j,N)if(!at2(S,j))amin(res,dist(i,j)+f(f,S|pw2(j),k-1,j));
    if(i!=N)amin(res,dist(i,N)+f(f,S,K,N));
    return mem[S][k][i]=res;
  };
  pp(f(f,0,K,N));
}}