import sys
input = sys.stdin.readline

N, M = map(int, input().split())
G = [[] for i in range(N)]
s, t, k = map(int, input().split())
s, t = s - 1, t - 1
for i in range(M):
    u, v = map(int, input().split())
    u, v = u - 1, v - 1
    G[u].append(v)
    G[v].append(u)
    
from collections import deque
def bfs(G, s):
    Q = deque([s])
    N = len(G)
    dist = [-1] * N
    par = [-1] * N
    dist[s] = 0
    while Q:
        u = Q.popleft()
        for v in G[u]:
            if dist[v] != -1:
                continue
            dist[v] = dist[u] + 1
            par[v] = u
            Q.append(v)

    return dist

D = bfs(G, s)
if D[t] == -1:
    print("Unknown")
elif (D[t] - k) % 2:
    print("No")
elif D[t] <= k:
    print("Yes")
else:
    print("Unknown")