#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

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--;
	vector to(n, vector<int>());
	int cnt = 0;
	rep(i, m) {
		int a, b; cin >> a >> b;
		a--, b--;
		to[a].push_back(b);
		to[b].push_back(a);
		if (a == s || b == s)cnt++;
	}
	vector<int> dp(n, INF);
	dp[s] = 0;
	queue<int>q;
	q.emplace(s);
	while (!q.empty()) {
		int v = q.front();
		q.pop();
		for (auto nv : to[v]) {
			if (chmin(dp[nv], dp[v] + 1)) {
				q.push(nv);
			}
		}
	}
	if (s == t) {
		if (1 == k % 2)cout << "No" << endl;
		else if (cnt)cout << "Yes" << endl;
		else cout << "Unknown" << endl;
		return 0;
	}
	if (INF == dp[t]) cout << "Unknown" << endl;
	else if (dp[t] % 2 != k % 2) cout << "No" << endl;
	else if (dp[t] <= k) cout << "Yes" << endl;
	else cout << "Unknown" << endl;
	return 0;
}