import sys input = lambda :sys.stdin.readline()[:-1] ni = lambda :int(input()) na = lambda :list(map(int,input().split())) yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES") no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO") ####################################################################### n, m = na() s,t,k = na() s -= 1 t -= 1 g = [[] for i in range(n)] for i in range(m): a, b = na() g[a-1].append(b-1) g[b-1].append(a-1) if n == 1: No() exit() if n == 2: if s == t and m >= 1: if k % 2 == 0: Yes() else: No() elif s == t and m == 0: No() elif s != t and m >= 1: if k % 2: Yes() else: No() else: if k % 2: print("Unknown") else: No() from heapq import * INF = 10**18 def dijkstra(g, s, n): dist = [INF]*n hq = [(0, s)] dist[s] = 0 while hq: d, v = heappop(hq) if dist[v]!=d: continue for to in g[v]: c = 1 if dist[v] + c < dist[to]: dist[to] = dist[v] + c heappush(hq, (dist[to], to)) return dist dist = dijkstra(g, s, n) if dist[t] != INF and (dist[t]-k)%2: No() exit() if dist[t] == INF: print("Unknown") exit() if dist[t] <= k: Yes() else: print("Unknown")