/**
 * author:	t9unkubj
 * created:	2024-03-15 
 */

#include<bits/stdc++.h>

#ifdef t9unkubj
#define _GLIBCXX_DEBUG
#define dbg(x) cout<<__LINE__<<" "<<#x<<":="<<x<<endl;
#else 
#define dbg(x) 58
#endif

using namespace std;

//#include<atcoder/all>
//using namespace atcoder;
int main(){
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int n,m;
	cin>>n>>m;
	int s,t,k;
	cin>>s>>t>>k;
	s--,t--;
	vector<vector<int>>g(n);
	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);
	}
	int INF=2e9;
	vector<int>md(n,INF);
	queue<int>que;
	md[s]=0;
	que.push(s);
	while(que.size()){
		auto p=que.front();que.pop();
		for(auto x:g[p]){
			if(md[x]>md[p]+1)md[x]=md[p]+1,que.push(x);
		}
	}
	if(md[t]!=INF){
		if(md[t]%2!=k%2){
			cout<<"No"<<endl;
		}
		else if(md[t]<=k){
			cout<<"Yes"<<endl;
		}
		else assert(0);
	}
	else cout<<"Unknown"<<endl;
}