from sys import stdin
input = stdin.readline
from random import shuffle, randrange

class UnionFind:
    def __init__(self,n):
        self.n = n
        self.parent_size = [-1]*n
 
    def leader(self,a):
        if self.parent_size[a] < 0:
            return a
        self.parent_size[a] = self.leader(self.parent_size[a])
        return self.parent_size[a]
 
    def merge(self,a,b):
        x, y = self.leader(a), self.leader(b)
        if x == y:
            return 
        if abs(self.parent_size[x]) < abs(self.parent_size[y]):
            x, y = y, x
        self.parent_size[x] += self.parent_size[y]
        self.parent_size[y] = x
        return 
 
    def same(self,a,b):
        return self.leader(a) == self.leader(b)
 
    def size(self,a):
        return abs(self.parent_size[self.leader(a)])
 
    def groups(self):
        result = [[] for _ in range(self.n)]
        for i in range(self.n):
            result[self.leader(i)].append(i)
        return result

def dfs(n, p, NG):
    cnt = 0
    SUM = 0
    for v in NG[n]:
        if v == p: continue
        s, a = dfs(v, n, NG)
        SUM += s+a
        cnt ^= a
    cnt ^= S[n]
    return SUM, cnt

shikii = 1000

def func(idx, G):
    edge2 = []
    for u, v in edge:
        u, v = u-1, v-1
        if UF.leader(u) == idx:
            edge2.append((u, v))
    ans = 1<<60
    for _ in range(shikii):
        UF2 = UnionFind(N)
        shuffle(edge2)
        NG = [[] for _ in range(N)]
        for u, v in edge2:
            if not UF2.same(u, v):
                UF2.merge(u, v)
                NG[u].append(v)
                NG[v].append(u)
        ans = min(ans, dfs(G[idx][randrange(len(G[idx]))], -1, NG)[0])
    return ans

N, M = map(int, input().split())
edge = [list(map(int, input().split())) for _ in range(M)]
S = list(map(int, input().split()))

UF = UnionFind(N)
for u, v in edge:
    u, v = u-1, v-1
    UF.merge(u, v)

G = UF.groups()
for g in G:
    SUM = 0
    for n in g:
        SUM ^= S[n]
    if SUM == 1:
        exit(print(-1))

ans = 0
for i in range(N):
    if UF.leader(i) == i:
        ans += func(i, G)

print(ans)