class unif:
  def __init__(self,n):
    self.pare=[-1]*n
    self.size=[1]*n
  def root(self,x):
    while self.pare[x]!=-1:
      x=self.pare[x]
    return x
  def unite(self,u,v):
    rootu=self.root(u)
    rootv=self.root(v)
    if rootu!=rootv:
      if self.size[rootu]>=self.size[rootv]:
        self.pare[rootv]=rootu
        self.size[rootu]+=self.size[rootv]
      else:
        self.pare[rootu]=rootv
        self.size[rootv]+=self.size[rootu]
  def same(self,s,t):
    return self.root(s)==self.root(t)
N,M=map(int,input().split())
s,t,K=map(int,input().split())
G=[[] for i in range(N)]
Z=unif(N)
for i in range(M):
  a,b=map(int,input().split())
  G[a-1].append(b-1)
  G[b-1].append(a-1)
  Z.unite(a-1,b-1)
if Z.same(s-1,t-1)==False:
  print('Unknown')
  exit()
dist=[-1]*N
from collections import deque
S=deque()
p=[[0]*N for i in range(20)]
for i in range(N):
  if dist[i]>=0:
    continue
  dist[i]=0
  S.append(i)
  p[0][i]=i
  while S:
    x=S.popleft()
    for y in G[x]:
      if dist[y]>=0:
        continue
      dist[y]=dist[x]+1
      p[0][y]=x
      S.append(y)
for k in range(1,20):
  for i in range(N):
    p[k][i]=p[k-1][p[k-1][i]]
def LCA(x,y):
  a,b=x,y
  if dist[a]>dist[b]:
    a,b=b,a
  e=dist[b]-dist[a]
  for k in range(20):
    if (e>>k)&1:
      b=p[k][b]
  if a==b:
    return a
  for k in range(19,-1,-1):
    if p[k][a]!=p[k][b]:
      a=p[k][a]
      b=p[k][b]
  a=p[0][a]
  return a
s-=1
t-=1
if K%2!=(dist[s]-dist[t])%2:
  print('No')
  exit()
pos=LCA(s,t)
d=dist[s]+dist[t]-2*dist[pos]
if d>K:
  print('Unknown')
else:
  print('Yes')