#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
//using mint = modint998244353;

//多倍長整数//
//#include <boost/multiprecision/cpp_int.hpp>
//namespace mp = boost::multiprecision;
//using Bint = mp::cpp_int;

const int INF = 1e9;
const int MOD = 998244353;
const long long LINF = 4e18;

using ll = long long;
using vi = vector<int>;
using vl = vector<long long>;
using vs = vector<string>;
using vc = vector<char>;
using vb = vector<bool>;
using vvi = vector<vector<int>>;
using vvvi = vector<vector<vector<int>>>;
using vvvvi = vector<vector<vector<vector<int>>>>;
using vvl = vector<vector<long long>>;
using vvvl = vector<vector<vector<long long>>>;
using vvvvl = vector<vector<vector<vector<long long>>>>;
using vvc = vector<vector<char>>;
using vvb = vector<vector<bool>>;
using vvvb = vector<vector<vector<bool>>>;
using vvvvb = vector<vector<vector<vector<bool>>>>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define dump(x)  cout << #x << " = " << (x) << endl;
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define ALL(obj) (obj).begin(),(obj).end()
vvi g(2e5);
int n,m;
int s,t,k;
vb color(2e5,false);
vb vis(2e5,false);

void dfs(int cur,bool c){
	vis[cur] = true;
	color[cur] = c;
	for(int next : g[cur]){
		if(vis[next] == false){
			dfs(next,!c);
		}
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	cin >> n >> m;
	
	cin >> s >> t >> k;
	s--;t--;
	dsu uf(n);
	rep(i,m){
		int a,b;
		cin >> a >> b;
		a--;b--;
		uf.merge(a,b);
		g[a].push_back(b);
		g[b].push_back(a);
	}
	vi dist(n,INF);
	dist[s] = 0;
	queue<int> que;
	que.push(s);
	while(!que.empty()){
		int cur = que.front();
		que.pop();
		for(int next : g[cur]){
			if(dist[next] != INF) continue;
			dist[next] = dist[cur] + 1;
			que.push(next);
		}
	}
	if(dist[t] <= k && dist[t]%2 == k%2){
		cout << "Yes" << endl;
		return 0;
	}
	dfs(s,true);
	if(vis[t] == false){
		cout << "Unknown" << endl;
		return 0;
	}
	//assert(false);
	cout << "No" << endl;
	return 0;
	if(color[t]){
		if(k%2 == 0 && k >= 2){
			cout << "Unknown" << endl;
		}else{
			cout << "No" << endl;
		}
		return 0;
	}else{
		if(k%2 == 1 && k >= 1){
			cout << "Unknown" << endl;
		}else{
			cout << "No" << endl;
		}
		return 0;
	}
	return 0;
}