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)

    color = [-1] * (N + 1)
    components = [-1] * (N + 1)
    component_id = 0

    for node in range(1, N + 1):
        if color[node] == -1:
            q = deque()
            q.append(node)
            color[node] = 0
            components[node] = component_id
            while q:
                u = q.popleft()
                for v in adj[u]:
                    if color[v] == -1:
                        color[v] = color[u] ^ 1
                        components[v] = component_id
                        q.append(v)
                    else:
                        assert color[v] == (color[u] ^ 1)
            component_id += 1

    s_comp = components[s]
    t_comp = components[t]
    color_ok = False

    if s_comp != t_comp:
        color_ok = True
    else:
        if (color[s] + color[t]) % 2 == k % 2:
            color_ok = True
        else:
            color_ok = False

    if not color_ok:
        print("No")
        return

    visited = [False] * (N + 1)
    dist = [-1] * (N + 1)
    q = deque()
    q.append(s)
    dist[s] = 0
    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]:
                dist[v] = dist[u] + 1
                visited[v] = True
                q.append(v)

    if not found:
        print("Unknown")
        return

    d = dist[t]
    if k >= d and (k - d) % 2 == 0:
        print("Yes")
    else:
        print("Unknown")

if __name__ == "__main__":
    main()