import sys
input=sys.stdin.readline
sys.setrecursionlimit(10**6)
import heapq

ans=2<<28
def dfs(G,v,used,goal,cost):
    global ans
    if v==goal:
        ans=min(ans,cost)
        return
    used[v]=True
    for i in G[v]:
        if used[i[1]]:
            continue
        dfs(G,i[1],used,goal,cost+i[0])
    used[v]=False
def main():
    n,m=map(int,input().split())
    x,y=map(int,input().split())
    x,y=x-1,y-1
    l=[tuple(int(i) for i in input().split()) for _ in range(n)]
    g=[[] for _ in range(n)]
    visited=[False]*n
    
    for _ in range(m):
        p,q=map(int,input().split())
        p,q=p-1,q-1
        dis=((l[q][0]-l[p][0])**2+(l[q][1]-l[p][1])**2)**0.5
        g[p].append((dis,q))
        g[q].append((dis,p))
    dfs(g,x,visited,y,0)
    print(ans)

if __name__=="__main__":
    main()