import sys # sys.setrecursionlimit(1000005) # sys.set_int_max_str_digits(200005) int1 = lambda x: int(x)-1 pDB = lambda *x: print(*x, end="\n", file=sys.stderr) p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr) def II(): return int(sys.stdin.readline()) def LI(): return list(map(int, sys.stdin.readline().split())) def LLI(rows_number): return [LI() for _ in range(rows_number)] def LI1(): return list(map(int1, sys.stdin.readline().split())) def LLI1(rows_number): return [LI1() for _ in range(rows_number)] def SI(): return sys.stdin.readline().rstrip() dij = [(0, 1), (-1, 0), (0, -1), (1, 0)] # dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)] # inf = -1-(-1 << 31) inf = -1-(-1 << 62) # md = 10**9+7 md = 998244353 from collections import deque n,m=LI() s,t,k=LI() s,t=s-1,t-1 to=[[] for _ in range(n)] for _ in range(m): u,v=LI1() to[u].append(v) to[v].append(u) dist=[-1]*n dist[s]=0 q=deque() q.append(s) while q: u=q.popleft() for v in to[u]: if dist[v]==-1: dist[v]=dist[u]+1 q.append(v) if dist[t]==-1: print("Unknown") elif dist[t]&1==k&1: if dist[t]<=k: print("Yes") else: print("Unknown") else: print("No")