n,m=map(int,input().split())
start,goal,k=map(int,input().split())
start-=1
goal-=1
e=[[] for i in range(n)]
for i in range(m):
  a,b=map(int,input().split())
  a-=1
  b-=1
  e[a]+=[b]
  e[b]+=[a]
v=[-1]*n
c=0
for i in range(n):
  if v[i]==-1:
    q=[i]
    v[i]=c
    for s in q:
      for t in e[s]:
        if v[t]==-1:
          q+=[t]
          v[t]=v[s]^1
    c+=2
if v[start]//2!=v[goal]//2:
  print("Unknown")
else:
  if (v[start]-v[goal])%2!=k%2:
    print("No")
  else:
    v=[-1]*n
    q=[start]
    v[start]=0
    for s in q:
      for t in e[s]:
        if v[t]==-1:
          q+=[t]
          v[t]=v[s]+1
    if v[goal]<=k:
      print("Yes")
    else:
      print("Unknown")