#include<stdio.h>

 #include<string.h>

 #include<math.h>

 const int maxn = ;

 const int INF=<<;

 double dis[maxn][maxn];

 struct node

 {

     double x;

     double y;

 } f[maxn];//储存每个点的坐标

 int n,m;

 void init()

 {

     for (int i = ; i <= n; i ++)

     {

         for (int j = ; j <= n; j ++)

         {

             dis[i][j] = INF;

         }

         dis[i][i] = ;

     }

 }

 void floyd()

 {

     int i,j,k;

     for (k = ; k <= n; k ++)

     {

         for (i = ; i <= n; i ++)

         {

             for (j = ; j <= n; j ++)

             {

                 if(dis[i][j] > dis[i][k] + dis[k][j])//更新距离

                     dis[i][j] = dis[i][k] + dis[k][j];

             }

         }

     }

 }

 int main()

 {

     scanf("%d",&n);

     init();

     for (int i = ; i <= n; i ++)

     {

         scanf("%lf%lf",&f[i].x,&f[i].y);

     }

     scanf("%d",&m);

     int u,v;

     while(m--)

     {

         scanf("%d%d",&u,&v);

         double d = sqrt((f[u].x-f[v].x)*(f[u].x-f[v].x)+(f[u].y-f[v].y)*(f[u].y-f[v].y));//计算u、v 之间的距离

         if (dis[u][v] > d) // 判断重边

         {

             dis[u][v] = d;

             dis[v][u] = d;

         }

     }

     int s,e;

     scanf("%d%d",&s,&e);

     floyd();

     printf("%.2f\n",dis[s][e]);

     return ;

 }