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

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

    # Compute bipartition
    color = [-1] * (N + 1)
    for u in range(1, N + 1):
        if color[u] == -1:
            q = deque()
            q.append(u)
            color[u] = 0
            while q:
                v = q.popleft()
                for nei in edges[v]:
                    if color[nei] == -1:
                        color[nei] = color[v] ^ 1
                        q.append(nei)
                    elif color[nei] == color[v]:
                        pass  # F is bipartite, so this won't happen

    same_partition = (color[s] == color[t])
    required_parity = 0 if same_partition else 1
    if k % 2 != required_parity:
        print("No")
        return

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

    # Compute minimal path length
    distance = [-1] * (N + 1)
    distance[s] = 0
    q = deque([s])
    while q:
        u = q.popleft()
        if u == t:
            break
        for v in edges[u]:
            if distance[v] == -1:
                distance[v] = distance[u] + 1
                q.append(v)
    l = distance[t]

    if l <= k and (k - l) % 2 == 0:
        print("Yes")
    else:
        print("Unknown")

if __name__ == "__main__":
    main()