towns / Pythone_towns

#!/usr/bin/python

# -*- coding: iso-8859-15 -*-

import os,sys

sys.stdin = open("maxdist.in")

sys.stdout = open("maxdist.out", "w")


N = int(input())

Inf = 1e10

A = [[Inf]*N for i in xrange(N)]

for i in xrange(N): A[i][i] = 0

C = [map(int,raw_input().split()) for i in range(N)]


from math import sqrt


M = int(raw_input())

for k in xrange(M):

i,j = map(int,raw_input().split())

i -= 1

j -= 1

if i!=j:

    A[i][j] = sqrt( (C[i][0]-C[j][0])**2 + (C[i][1]-C[j][1])**2 )

    A[j][i] = A[i][j]


for k in xrange(N):

    for i in xrange(N):

        for j in xrange(N):

            if j > i:

                t = A[i][k] + A[k][j]

                if t < A[i][j]:

                    A[i][j] = t

                    A[j][i] = t



maxdist = max(map(max,A))


print -1 if maxdist == Inf else maxdist