from scipy.sparse.csgraph import dijkstra
from scipy.sparse import csr_matrix

int1 = lambda x: int(x) - 1
N, M = map(int, input().split())
X, Y = map(int1, input().split())

P = [tuple(map(int, input().split())) for _ in range(N)]
length, frm, to = [], [], []
for _ in range(M):
    p, q = map(int1, input().split())
    length.append(((P[p][0] - P[q][0]) ** 2 + (P[p][1] - P[q][1]) ** 2) ** .5)
    frm.append(p)
    to.append(q)

matr = csr_matrix((length, (frm, to)), shape=(N, N))
print(dijkstra(matr, indices=X, directed=False)[Y])