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])
    t = int(input[ptr+1])
    k = int(input[ptr+2])
    ptr += 3

    edges = [[] for _ in range(N)]
    for _ in range(M):
        a = int(input[ptr]) - 1
        b = int(input[ptr+1]) - 1
        edges[a].append(b)
        edges[b].append(a)
        ptr += 2

    if s == t:
        if k % 2 != 0:
            print("No")
        else:
            s_node = s - 1
            if len(edges[s_node]) == 0:
                print("No")
            else:
                print("Yes")
        return

    color = [-1] * N
    for i in range(N):
        if color[i] == -1:
            color[i] = 0
            q = deque([i])
            while q:
                u = q.popleft()
                for v in edges[u]:
                    if color[v] == -1:
                        color[v] = color[u] ^ 1
                        q.append(v)

    s_color = color[s-1]
    t_color = color[t-1]
    if (s_color + t_color + k) % 2 != 0:
        print("No")
        return

    visited = [False] * N
    q = deque([s-1])
    visited[s-1] = True
    distance = {s-1: 0}
    found = False

    while q:
        u = q.popleft()
        for v in edges[u]:
            if not visited[v]:
                visited[v] = True
                distance[v] = distance[u] + 1
                if v == t-1:
                    found = True
                    q = deque()
                    break
                q.append(v)

    if not visited[t-1]:
        print("Unknown")
    else:
        d = distance[t-1]
        if k >= d and (k - d) % 2 == 0:
            print("Yes")
        else:
            print("Unknown")

if __name__ == "__main__":
    main()