from heapq import *

N,M = map(int,input().split())
X,Y = map(int,input().split())
P = [list(map(int,input().split())) for _ in range(N)]
E = [[] for _ in range(N)]
for i in range(M):
    u,v = map(int,input().split())
    u -= 1
    v -= 1
    d = ((P[u][0] - P[v][0]) ** 2 + (P[u][1] - P[v][1]) ** 2) ** 0.5
    E[u].append((v,d))
    E[v].append((u,d))
INF = 10 ** 10

def dijkstra(x,y):
    D = [INF] * N
    D[x] = 0
    q = [(0,x)]
    while q:
        d, u = heappop(q)
        if d > D[u]: continue
        for a,b in E[u]:
            if D[a] > D[u] + b:
                D[a] = D[u] + b
                heappush(q, (D[a], a))
    return D[y]

print(dijkstra(X-1,Y-1))