import sys
from collections import deque

def main():
    sys.setrecursionlimit(1 << 25)
    N, M = map(int, sys.stdin.readline().split())
    s, t, k = map(int, sys.stdin.readline().split())
    edges = [[] for _ in range(N+1)]  # 1-based indexing
    for _ in range(M):
        a, b = map(int, sys.stdin.readline().split())
        edges[a].append(b)
        edges[b].append(a)
    
    # Bipartite coloring
    color = [-1] * (N+1)
    for start in range(1, N+1):
        if color[start] == -1:
            color[start] = 0
            q = deque([start])
            while q:
                u = q.popleft()
                for v in edges[u]:
                    if color[v] == -1:
                        color[v] = color[u] ^ 1
                        q.append(v)
    
    # Check parity of k against color difference
    if (color[s] == color[t]) != (k % 2 == 0):
        print("No")
        return
    
    # BFS to find shortest path in F
    visited = [-1] * (N+1)
    q = deque([s])
    visited[s] = 0
    found = False
    while q:
        u = q.popleft()
        if u == t:
            found = True
            break
        for v in edges[u]:
            if visited[v] == -1:
                visited[v] = visited[u] + 1
                q.append(v)
    
    if found:
        l = visited[t]
        if k >= l and (k - l) % 2 == 0 and (M >= 1 or k == l):
            print("Yes")
        else:
            print("Unknown")
    else:
        if color[s] == color[t]:
            print("No")
        else:
            if k >= 1 and (k - 1) % 2 == 0:
                print("Unknown")
            else:
                print("No")

if __name__ == "__main__":
    main()