import sys

# sys.setrecursionlimit(1000005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

from collections import deque

n,m=LI()
s,t,k=LI()
s,t=s-1,t-1
to=[[] for _ in range(n)]
for _ in range(m):
    u,v=LI1()
    to[u].append(v)
    to[v].append(u)

dist=[-1]*n
dist[s]=0
q=deque()
q.append(s)
while q:
    u=q.popleft()
    for v in to[u]:
        if dist[v]==-1:
            dist[v]=dist[u]+1
            q.append(v)

if dist[t]==-1:
    print("Unknown")
elif dist[t]&1==k&1:
    if dist[t]<=k:
        print("Yes")
    else:
        print("Unknown")
else:
    print("No")