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]); t = int(input[idx+1]); k = int(input[idx+2]); idx +=3
    s -= 1  # converting to 0-based
    t -= 1

    # Build adjacency list
    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

    # BFS to find shortest path from s to t
    INF = float('inf')
    dist = [INF] * N
    dist[s] = 0
    q = deque([s])
    while q:
        u = q.popleft()
        for v in adj[u]:
            if dist[v] == INF:
                dist[v] = dist[u] + 1
                q.append(v)
                if v == t:
                    q = deque()  # early exit
                    break

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

if __name__ == "__main__":
    main()