import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        group_members = collections.defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return ''.join(f'{r}: {m}' for r, m in self.all_group_members().items())
input = sys.stdin.readline
n,m = map(int,input().split())
s,t,k = map(int,input().split())
if n == 1:
    if k == 0:
        print('Yes')
    else:
        print('No')
    exit()
if n == 2:
    if s != t and k % 2 == 0:
        print('No')
        exit()
    if s == t and k % 2 == 1:
        print('No')
        exit()

   



uf = UnionFind(n)
edge = [[] for i in range(n)]
for i in range(m):
    u,v = map(int,input().split())
    u-=1
    v-=1
    edge[u].append(v)
    edge[v].append(u)
    uf.union(u,v)
s -= 1
t -= 1
if s == t:
    if len(edge[s]) >= 1 and k % 2 == 0:
        print('Yes')
        exit()
    elif len(edge[s]) == 0 and k % 2 == 0:
        print('Unknown')
        exit()
    elif k % 2 == 1:
        print('No')
        exit()
if uf.same(s,t) == False:
    print('Unknown')
    exit()
start = s
d = collections.deque()
dist = [10**18 for i in range(n)]
color = [0 for i in range(n)]
d.append(start)
dist[start] = 0
while d:
    now = d.popleft()
    for i in edge[now]:
        color[i] = color[now] ^ 1
        if dist[i] > dist[now] + 1:
            dist[i] = dist[now] + 1
            d.append(i)
if color[s] == color[t]:
    if k % 2 == 0 and dist[t] <= k:
        print('Yes')
        exit()
    if k % 2 != 0:
        print('No')
        exit()
if color[s] != color[t]:
    if k % 2 == 1 and dist[t] <= k:
        print('Yes')
        exit()
    if k % 2 != 1:
        print('No')
        exit()
print('Unknown')