import sys
from collections import deque

def main():
    input = sys.stdin.read().split()
    idx = 0
    N = int(input[idx]); idx +=1
    M = int(input[idx]); idx +=1
    s = int(input[idx])-1; t = int(input[idx+1])-1; k = int(input[idx+2]); idx +=3
    adj = [[] for _ in range(N)]
    for _ in range(M):
        a = int(input[idx])-1; b = int(input[idx+1])-1
        adj[a].append(b)
        adj[b].append(a)
        idx +=2
    
    color = [-1] * N
    dist = [-1] * N
    q = deque()
    q.append(s)
    color[s] = 0
    dist[s] = 0
    while q:
        u = q.popleft()
        for v in adj[u]:
            if color[v] == -1:
                color[v] = color[u] ^ 1
                dist[v] = dist[u] + 1
                q.append(v)
            elif color[v] == color[u]:
                pass
    
    if dist[t] == -1:
        print("Unknown")
        return
    
    parity_diff = (color[s] + color[t]) % 2
    if parity_diff != k % 2:
        print("No")
        return
    
    d = dist[t]
    if d <= k:
        print("Yes")
    else:
        print("Unknown")

if __name__ == "__main__":
    main()