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)]
for _ in range(M):
    A, B = map(int, input().split())
    G[A-1].append(B-1)
    G[B-1].append(A-1)

if N == 1:
    exit(print("No"))
elif N == 2:
    if k%2 == 1:
        if M == 1:
            print("Yes")
        else:
            print("Unknown")
    else:
        print("No")

visited = [-1]*N
visited[s] = 0
que = deque()
que.append(s)
same = False
while que:
    n = que.popleft()
    if n == t:
        same = True
    for v in G[n]:
        if visited[v] == -1:
            visited[v] = visited[n]^1
            que.append(v)

if same:
    if visited[t]%2 == k%2:
        visited = [-1]*N
        visited[s] = 0
        que = deque()
        que.append(s)
        while que:
            n = que.popleft()
            for v in G[n]:
                if visited[v] == -1:
                    visited[v] = visited[n]+1
                    que.append(v)
        if visited[t] <= k:
            print("Yes")
        else:
            print("Unknown")
    else:
        print("No")
else:
    print("Unknown")