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


n, m = map(int,input().split())
s, t, k = map(int,input().split())
s -= 1
t -= 1

if n == 1:
	print("No")
	exit()

ikeru = [[] for i in range(n)]
uf = UnionFind(n)
for i in range(m):
	a, b = map(int,input().split())
	a -= 1
	b -= 1
	ikeru[a].append(b)
	ikeru[b].append(a)
	uf.union(a, b)

if n == 2:
	if s == t:
		if k % 2 == 1:
			print("No")
			exit()
		if uf.find(0) != uf.find(1):
			print("Unknown")
			exit()
		print("Yes")
	else:
		if k % 2 == 0:
			print("No")
			exit()
		if uf.find(0) != uf.find(1):
			print("Unknown")
			exit()
		print("Yes")
	exit()

if uf.find(s) != uf.find(t):
	print("Unknown")
	exit()

from collections import deque

dst = [0] * n
tansaku = [0] * n
tansaku[s] = 1
mada = deque([])
mada.append(s)

while mada:
	i = mada.popleft()
	for j in ikeru[i]:
		if tansaku[j] == 0:
			tansaku[j] = 1
			mada.append(j)
			dst[j] = dst[i] + 1

if dst[t] % 2 != k % 2:
	print("No")
	exit()

if dst[t] <= k:
	print("Yes")
	exit()

print("Unknown")