#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	
	int N,M;
	cin>>N>>M;
	int S,T,K;
	cin>>S>>T>>K;
	S--,T--;
	int s = S,t = T;
	vector<int> a(M),b(M);
	vector<vector<int>> E(N);
	rep(i,M){
		cin>>a[i]>>b[i];
		a[i]--,b[i]--;
		E[a[i]].push_back(b[i]);
		E[b[i]].push_back(a[i]);
	}
	vector<int> d(N,Inf32);
	d[s] = 0;
	queue<int> Q;
	Q.push(s);
	while(Q.size()>0){
		int u = Q.front();
		Q.pop();
		rep(i,E[u].size()){
			int v = E[u][i];
			if(d[v]!=Inf32)continue;
			d[v] = d[u]+1;
			Q.push(v);
		}
	}
	
	bool f0 = false,f1 = false;
	{
		if(d[t] %2 == K%2 && d[t] <= K)f0 = true;
		if(s==t && K%2==0 && E[s].size()==0)f0 = false;
	}
	
	if(N==1)f1 = false;
	else{
		if(s==t){
			if(K%2==0)f1 = true;
		}
		else{
			if(N==2){
				if(K%2==1)f1 = true;
			}
			else{
				if(d[t]==Inf32)f1 = true;
				else if(d[t]%2==K%2)f1 = true;
				
			}
		}
		
	}
	if(f0)cout<<"Yes"<<endl;
	else if(!f1)cout<<"No"<<endl;
	else cout<<"Unknown"<<endl;
	return 0;
}