import sys
import heapq
sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


class Dijkstra_list():  # 1-based
    def __init__(self,N):
        self.N = N
        self.edges = [[] for _ in range(N+1)]

    def add(self, u, v, d, directed=False):
        if directed is False:  # 無向グラフの場合
            self.edges[u].append((v,d))
            self.edges[v].append((u,d))
        else:  # 有向グラフの場合
            self.edges[u].append((v,d))

    def delete(self, u, v):
        self.edges[u] = [_ for _ in self.edges[u] if _[0] != v]
        self.edges[v] = [_ for _ in self.edges[v] if _[0] != u]

    def search(self, s):  # sから各頂点までの最短距離
        inf = 10**18
        dist = [inf]*(self.N+1)
        dist[s] = 0
        q = []
        heapq.heappush(q, (0, s))
        v = [0]*(self.N+1)
        while q:
            k, u = heapq.heappop(q)
            if v[u]:
                continue
            v[u] = 1

            for uv, ud in self.edges[u]:
                if v[uv]:
                    continue
                vd = k + ud
                if dist[uv] > vd:
                    dist[uv] = vd
                    heapq.heappush(q, (vd, uv))
        return dist


N,M = MI()
X,Y = MI()
pos = [(0,0)]+[tuple(MI()) for _ in range(N)]

Di = Dijkstra_list(N)
for _ in range(M):
    P,Q = MI()
    x0,y0 = pos[P]
    x1,y1 = pos[Q]
    d = ((x0-x1)**2+(y0-y1)**2)**.5
    Di.add(P,Q,d,directed=False)

dist = Di.search(X)
ans = dist[Y]
print(ans)