from collections import deque

n, m = map(int, input().split())
s, t, k = map(int, input().split())
if n == 1:
    print("No")
    exit()
s -= 1
t -= 1
edges = [[] for _ in range(n)]
for _ in range(m):
    u, v = map(int, input().split())
    u -= 1
    v -= 1
    edges[u].append(v)
    edges[v].append(u)

queue = deque()
dist = [-1] * n
dist[s] = 0
queue.append(s)
while queue:
    pos = queue.popleft()
    for npos in edges[pos]:
        if dist[npos] != -1:
            continue
        dist[npos] = dist[pos] + 1
        queue.append(npos)

if dist[t] == -1:
    print("Unknown")
elif dist[t] % 2 != k % 2:
    print("No")
elif dist[t] <= k:
    print("Yes")
else:
    print("Unknown")