import sys
from collections import deque

def main():
    N, M = map(int, sys.stdin.readline().split())
    s, t, k = map(int, sys.stdin.readline().split())
    edges = [[] for _ in range(N+1)]
    for _ in range(M):
        a, b = map(int, sys.stdin.readline().split())
        edges[a].append(b)
        edges[b].append(a)
    
    color = [-1] * (N+1)
    distance = [-1] * (N+1)
    q = deque()
    q.append(s)
    color[s] = 0
    distance[s] = 0
    found = False
    while q and not found:
        u = q.popleft()
        for v in edges[u]:
            if color[v] == -1:
                color[v] = color[u] ^ 1
                distance[v] = distance[u] + 1
                q.append(v)
                if v == t:
                    d = distance[v]
                    found = True
                    break

    if color[s] == color[t]:
        if k % 2 != 0:
            print("No")
            return
    else:
        if k % 2 == 0:
            print("No")
            return

    if d == -1:
        print("Unknown")
    else:
        if d <= k and (k - d) % 2 == 0:
            print("Yes")
        else:
            print("Unknown")

if __name__ == "__main__":
    main()