import sys
input = sys.stdin.readline

N,M=map(int,input().split())
s,t,k=map(int,input().split())
s-=1
t-=1

E=[[] for i in range(N)]

for i in range(M):
    u,v=map(int,input().split())
    u-=1
    v-=1
    E[u].append(v)
    E[v].append(u)

DIS=[-1]*N
Q=[s]
DIS[s]=0
LIST=[]

while Q:
    x=Q.pop()
    LIST.append(x)
    for to in E[x]:
        if DIS[to]==-1:
            DIS[to]=DIS[x]+1
            Q.append(to)

if 0<=DIS[t]<=k and len(LIST)>1:
    if (DIS[t]-k)%2==0:
        print("Yes")
    else:
        print("No")
    exit()

if DIS[t]>k and len(LIST)>1:
    if (DIS[t]-k)%2==0:
        print("Unknown")
    else:
        print("No")
    exit()

if DIS[t]==0 and len(LIST)==1:
    if N==1:
        if k==0:
            print("Yes")
        else:
            print("No")
    else:
        if k==0:
            print("Yes")
        elif k%2==0:
            print("Unknown")
        else:
            print("No")

    exit()

DIS2=[-1]*N
Q=[t]
DIS2[t]=0
LIST2=[]

while Q:
    x=Q.pop()
    LIST2.append(x)
    for to in E[x]:
        if DIS2[to]==-1:
            DIS2[to]=DIS2[x]+1
            Q.append(to)


if len(LIST)==1 and len(LIST2)==1:
    if k%2==0:
        print("No")
    else:
        print("Unknown")
else:
    print("Unknown")