#include<cstdio>

 #include<cstdlib>

 #include<cmath>

 #include<cstring>

 #include<algorithm>

 #include<iostream>

 #include<vector>

 #include<map>

 #include<set>

 #include<queue>

 #include<string>

 #define inf 1000000000

 #define maxn 500

 #define maxm 500+100

 #define eps 1e-10

 #define ll long long

 #define pa pair<int,int>

 #define for0(i,n) for(int i=0;i<=(n);i++)

 #define for1(i,n) for(int i=1;i<=(n);i++)

 #define for2(i,x,y) for(int i=(x);i<=(y);i++)

 #define for3(i,x,y) for(int i=(x);i>=(y);i--)

 #define mod 1000000007

 #define sqr(x) (x)*(x)

 using namespace std;

 inline int read()

 {

     int x=,f=;char ch=getchar();

     while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

     while(ch>=''&&ch<=''){x=*x+ch-'';ch=getchar();}

     return x*f;

 }

 int n,t,k;

 struct rec{double x,y;}a[maxn];

 double c[maxn][maxn],d[maxn][maxn];

 queue<pa>q;

 bool v[maxn][maxn];

 int main()

 {

     freopen("input.txt","r",stdin);

     freopen("output.txt","w",stdout);

     n=read();t=read();k=read();

     for0(i,n)a[i].x=read(),a[i].y=read();

     for0(i,n)for0(j,n)c[i][j]=sqrt(sqr(a[i].x-a[j].x)+sqr(a[i].y-a[j].y));

     for0(i,n)for0(j,k)d[i][j]=inf;

     d[][]=;

     q.push(pa(,));

     while(!q.empty())

     {

         int x=q.front().first,y=q.front().second;q.pop();

         v[x][y]=;

         for1(i,n)

          if(i!=x&&d[x][y]+c[x][i]<d[i][y+])

          {

              d[i][y+]=d[x][y]+c[x][i];

              if(!v[i][y+]){v[i][y+]=;q.push(pa(i,y+));}

          }

     }

     double ans=inf;

     for1(i,n)if(i!=t)ans=min(ans,d[i][k]+c[i][t]);

     printf("%.2f\n",ans);

     return ;

 }