## https://yukicoder.me/problems/no/2674

from collections import deque

MAX_INT = 10 ** 18

def main():
    N, M= map(int ,input().split())
    s, t, k = map(int, input().split())
    s -= 1
    t -= 1
    next_nodes = [[] for _ in range(N)]
    for _ in range(M):
        a, b = map(int, input().split())
        next_nodes[a - 1].append(b - 1)
        next_nodes[b - 1].append(a - 1)

    passed = [-1] * N
    dists = [MAX_INT] * N
    queue = deque()
    queue.append(s)
    passed[s] = 0
    dists[s] = 0
    while len(queue) > 0:
        v = queue.popleft()
        for w in next_nodes[v]:
            if passed[w] == -1:
                passed[w] = 1 - passed[v]
                dists[w] = 1 + dists[v]
                queue.append(w)

    if passed[t] == -1:
        print("Unknown")
        return

    # s とtが同じである場合
    if s == t:
        nown = 0
        for i in range(N):
            if passed[i] != -1:
                nown += 1
        if nown == 1:
            if k % 2 == 1:
                print("No")
            else:
                print("Unknown")
            return

    if passed[t] == 0:
        if k % 2 == 1:
            print("No")
        elif dists[t] <= k:
            print("Yes")
        else:
            print("Unknown")
    elif passed[t] == 1:
        if k % 2 == 0:
            print("No")
        elif dists[t] <= k:
            print("Yes")
        else:
            print("Unknown")


            







if __name__ == "__main__":
    main()