#include<iostream>
#include<vector>
#include<queue>
#include<cassert>
using namespace std;
int N,M;
vector<int>G[2<<17];
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int s,t,k;
	cin>>N>>M>>s>>t>>k;
	s--,t--;
	for(int i=0;i<M;i++)
	{
		int a,b;cin>>a>>b;
		a--,b--;
		G[a].push_back(b);
		G[b].push_back(a);
	}
	if(s==t)
	{
		if(N==1||k%2==1)cout<<"No\n";
		else
		{
			if(!G[s].empty())cout<<"Yes\n";
			else cout<<"Unknown\n";
		}
		return 0;
	}
	queue<int>Q;
	Q.push(s);
	vector<int>dist(N,(int)1e9);
	dist[s]=0;
	while(!Q.empty())
	{
		int u=Q.front();Q.pop();
		for(int v:G[u])
		{
			if(dist[v]>dist[u]+1)
			{
				dist[v]=dist[u]+1;
				Q.push(v);
			}
		}
	}
	if(dist[t]==(int)1e9)
	{
		if(k%2==1)cout<<"Unknown\n";
		else
		{
			if(N>=3)cout<<"Unknown\n";
			else cout<<"No\n";
		}
	}
	else if(dist[t]%2==1)
	{
		if(k%2==0)cout<<"No\n";
		else
		{
			if(dist[t]<=k)cout<<"Yes\n";
			else cout<<"Unknown\n";
		}
	}
	else
	{
		if(k%2==1)cout<<"No\n";
		else
		{
			if(dist[t]<=k)cout<<"Yes\n";
			else cout<<"Unknown\n";
		}
	}
}