from collections import deque

N, M = map(int, input().split())
S, T, K = map(int, input().split())
S, T = S - 1, T - 1
G = [[] for _ in range(N)]
INF = 10**9
for _ in range(M):
    A, B = map(int, input().split())
    A, B = A - 1, B - 1
    G[A].append(B)
    G[B].append(A)

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

D = [INF] * N
D[S] = 0
Q = deque()
Q.append(S)

while Q:
    now = Q.popleft()
    for nxt in G[now]:
        if D[nxt] > D[now] + 1:
            D[nxt] = D[now] + 1
            Q.append(nxt)

if S == T:
    if K % 2 == 0 and len(G[S]) > 0:
        print("Yes")
    else:
        print("No")
else:
    if D[T] <= K and D[T] % 2 == K % 2:
        print("Yes")
    elif D[T] == INF or (D[T] != INF and D[T] % 2 == K % 2):
        print("Unknown")
    else:
        print("No")