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]) - 1  # converting to 0-based
    ptr += 1
    t = int(input[ptr]) - 1
    ptr += 1
    k = int(input[ptr])
    ptr += 1

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

    # BFS to compute distance and bipartition
    visited = [False] * N
    color = [-1] * N
    distance = [-1] * N
    q = deque()
    q.append(s)
    visited[s] = True
    color[s] = 0
    distance[s] = 0

    while q:
        u = q.popleft()
        for v in adj[u]:
            if not visited[v]:
                visited[v] = True
                color[v] = 1 - color[u]
                distance[v] = distance[u] + 1
                q.append(v)
            else:
                # Check bipartition consistency (though problem states F is bipartite)
                if color[v] == color[u]:
                    print("No")
                    return

    if not visited[t]:
        # s and t are in different components
        print("Unknown")
        return

    # Check parity
    required_parity = distance[t] % 2
    if k % 2 != required_parity:
        print("No")
        return

    # Check if k >= d and (k - d) is even
    d = distance[t]
    if k >= d and (k - d) % 2 == 0:
        print("Yes")
    else:
        print("Unknown")

if __name__ == "__main__":
    main()