import sys
from collections import deque

def main():
    sys.setrecursionlimit(1 << 25)
    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)

    color = [-1] * (N+1)
    color[s] = 0
    q = deque()
    q.append(s)
    while q:
        u = q.popleft()
        for v in adj[u]:
            if color[v] == -1:
                color[v] = color[u] ^ 1
                q.append(v)
            else:
                if color[v] == color[u]:
                    pass

    s_color = color[s]
    t_color = color[t]
    if s_color == -1 or t_color == -1:
        print("No")
        return

    if (s_color == t_color and k % 2 != 0) or (s_color != t_color and k % 2 !=1):
        print("No")
        return

    visited = [False] * (N+1)
    q = deque()
    q.append(s)
    visited[s] = True
    found = False
    while q:
        u = q.popleft()
        if u == t:
            found = True
            break
        for v in adj[u]:
            if not visited[v]:
                visited[v] = True
                q.append(v)
    if not found:
        print("Unknown")
        return

    dist = [-1] * (N+1)
    dist[s] =0
    q = deque()
    q.append(s)
    while q:
        u = q.popleft()
        for v in adj[u]:
            if dist[v] == -1:
                dist[v] = dist[u] +1
                q.append(v)
    d = dist[t]
    if k >= d and (k % 2) == (d % 2):
        print("Yes")
    else:
        print("Unknown")

if __name__ == "__main__":
    main()