import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

n,m = map(int,input().split())

graph = [[] for i in range(n+1)]
e = []
for i in range(m):
  a,b = map(int,input().split())
  graph[a].append(b)
  graph[b].append(a)
  e.append([a-1, b-1])

c = list(map(int,input().split()))
ini = 0
for i in range(n):
  if c[i]:
    ini |= (1<<i)

m1 = m//2
m2 = m - m1
e1,e2 = e[:m1], e[m1:]
d1, d2 = defaultdict(lambda : 10**15),defaultdict(lambda : 10**15)

s1,s2 = set(),set()
for i in range(2):
  for bit in range(1<<m1):
    now = 0
    cnt = 0
    for i in range(m1):
      if (bit >> i) & 1:
        now ^= 1<<e1[i][0]
        now ^= 1<<e1[i][1]
        cnt += 1
    s1.add(now)
    d1[now] = min(d1[now], cnt)
  m1,m2 = m2,m1
  e1,e2 = e2,e1
  s1,s2 = s2,s1
  d1,d2 = d2,d1

ans = 10**15
for i in s1:
  if (ini ^ i) in s2:
    ans = min(ans, d1[i] + d2[ini^i])

print(ans) if ans < 10**15 else print(-1)