n, m = map(int, input().split())
s, t, k = map(int, input().split())
s -= 1
t -= 1
adj = [[] for i in range(n)]
for i in range(m):
	u, v = map(int, input().split())
	u -= 1
	v -= 1
	adj[u].append(v)
	adj[v].append(u)

dis = [1000000000 for i in range(n)]

from queue import *
q = Queue()

q.put(s)
dis[s] = 0

while not q.empty():
	u = q.get()
	q.task_done()
	for v in adj[u]:
		if dis[v] > dis[u] + 1:
			dis[v] = dis[u] + 1
			q.put(v)

if dis[t] < 1000000000:
	if (dis[t] + k) % 2:
		print("No")
	elif dis[t] <= k:
		print("Yes")
	else:
		print("Unknown")
elif k % 2:
	print("Unknown")
else:
	print("No" if n == 2 else "Unknown")