import sys
from collections import deque

def main():
    input = sys.stdin.read().split()
    ptr = 0
    N = int(input[ptr])
    ptr += 1
    M = int(input[ptr])
    ptr += 1
    s = int(input[ptr])
    ptr += 1
    t = int(input[ptr])
    ptr += 1
    k = int(input[ptr])
    ptr += 1

    adj = [[] for _ in range(N + 1)]
    for _ in range(M):
        a = int(input[ptr])
        ptr += 1
        b = int(input[ptr])
        ptr += 1
        adj[a].append(b)
        adj[b].append(a)

    # BFS to find distance from s to t and check connectivity
    visited = [-1] * (N + 1)
    q = deque()
    q.append(s)
    visited[s] = 0
    found = False
    while q:
        u = q.popleft()
        if u == t:
            found = True
            break
        for v in adj[u]:
            if visited[v] == -1:
                visited[v] = visited[u] + 1
                q.append(v)
    
    if not found:
        print("Unknown")
        return
    
    d = visited[t]
    if (d % 2) != (k % 2):
        print("No")
    elif k >= d:
        print("Yes")
    else:
        if d % 2 == 1:
            print("Unknown")
        else:
            print("No")

if __name__ == "__main__":
    main()