/*
このコード、と～おれ!
Be accepted!
∧＿∧　
（｡･ω･｡)つ━☆・*。
⊂　　 ノ 　　　・゜+.
　しーＪ　　　°。+ *´¨)
 　　　　　　　　　.· ´¸.·*´¨) ¸.·*¨)
		  　　　　　　　　　　(¸.·´ (¸.·'* ☆
*/

#include <cstdio>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstring>
#include <vector>
#include <numeric>
#include <iostream>
#include <random>
#include <map>
#include <unordered_map>
#include <queue>
#include <regex>
#include <functional>
#include <complex>
#include <list>
#include <cassert>
#include <iomanip>
#include <set>
#include <stack>
#include <bitset>
#include <array>
#include <chrono>
#include <unordered_set>

//#pragma GCC target("arch=skylake-avx512")
//#pragma GCC target("avx2")
//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse4")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define repeat(i, n, m) for(int i = n; i < (m); ++i)
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define printynl(a) printf(a ? "yes\n" : "no\n")
#define printyn(a) printf(a ? "Yes\n" : "No\n")
#define printYN(a) printf(a ? "YES\n" : "NO\n")
#define printim(a) printf(a ? "possible\n" : "imposible\n")
#define printdb(a) printf("%.50lf\n", a)
#define printLdb(a) printf("%.50Lf\n", a)
#define printdbd(a) printf("%.16lf\n", a)
#define prints(s) printf("%s\n", s.c_str())
#define all(x) (x).begin(), (x).end()
#define deg_to_rad(deg) (((deg)/360.0L)*2.0L*PI)
#define rad_to_deg(rad) (((rad)/2.0L/PI)*360.0L)
#define Please return
#define AC 0
#define manhattan_dist(a, b, c, d) (abs(a - c) + abs(b - d))

using ll = long long;
using ull = unsigned long long;

constexpr int INF = 1073741823;
constexpr int MINF = -1073741823;
constexpr ll LINF = ll(4661686018427387903);
constexpr ll MOD = 1e9 + 7;
constexpr ll mod = 998244353;
constexpr long double eps = 1e-14;
const long double PI = acosl(-1.0L);

using namespace std;

void scans(string& str) {
	char c;
	str = "";
	scanf("%c", &c);
	if (c == '\n')scanf("%c", &c);
	while (c != '\n' && c != -1 && c != ' ') {
		str += c;
		scanf("%c", &c);
	}
}

void scanc(char& str) {
	char c;
	scanf("%c", &c);
	if (c == -1)return;
	while (c == '\n') {
		scanf("%c", &c);
	}
	str = c;
}

double acot(double x) {
	return PI / 2 - atan(x);
}

ll LSB(ll n) { return (n & (-n)); }

template<typename T>
inline T chmin(T& a, const T& b) {
	if (a > b)a = b;
	return a;
}

template<typename T>
inline T chmax(T& a, const T& b) {
	if (a < b)a = b;
	return a;
}

//cpp_int
#if __has_include(<boost/multiprecision/cpp_int.hpp>)
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using namespace boost::multiprecision;
#else
using cpp_int = ll;
#endif

//atcoder library
#if __has_include(<atcoder/all>)
#include <atcoder/all>
//using namespace atcoder;
#endif

/*
	random_device seed_gen;
	mt19937 engine(seed_gen());
	uniform_int_distribution dist(1, 100);
*/


/*----------------------------------------------------------------------------------*/

/*
* @title template(graph)
* @docs kyopro/docs/graph_template.md
*/

template<typename T>
struct edge {
	T cost;
	int from, to;

	edge(int from, int to) : from(from), to(to), cost(T(1)) {}
	edge(int from, int to, T cost) : from(from), to(to), cost(cost) {}
};

template<typename T = int>
struct graph {

	int n;
	bool directed, weighted;

	vector<vector<edge<T>>> g;

	graph(int n, bool directed, bool weighted) : g(n), n(n), directed(directed), weighted(weighted) {}

	void add_edge(int from, int to, T cost = T(1)) {
		g[from].emplace_back(from, to, cost);
		if (not directed) {
			g[to].emplace_back(to, from, cost);
		}
	}

	vector<edge<T>>& operator[](const int& idx) {
		return g[idx];
	}

	void read(int e, bool one_indexed) {
		int a, b, c = 1;
		while (e--) {
			scanf("%d%d", &a, &b);
			if (weighted) {
				scanf("%d", &c);
			}
			if (one_indexed)--a, --b;
			add_edge(a, b, c);
		}
	}

	void read(int e, bool one_indexed, const string& format) {
		int a, b;
		T c = T(1);
		while (e--) {
			scanf("%d%d", &a, &b);
			if (weighted) {
				scanf(format.c_str(), &c);
			}
			if (one_indexed)--a, --b;
			add_edge(a, b, c);
		}
	}

};

/*
* @title dijkstra
* @docs kyopro/docs/dijkstra.md
*/


template<typename T = int>
vector<T> dijkstra(graph<T>& g, const int& v, const int& n, const T Inf) {
	priority_queue<pair<T, int>, vector<pair<T, int>>, greater<pair<T, int>>> priq;
	vector<T> res(n);
	fill(all(res), Inf);
	priq.push({ 0, v });
	res[v] = 0;
	int top;
	while (!priq.empty()) {
		top = priq.top().second;
		T cost = priq.top().first;
		priq.pop();
		if (cost > res[top])continue;
		for (const auto& aa : g[top]) {
			if (res[top] + aa.cost >= res[aa.to])continue;
			res[aa.to] = aa.cost + res[top];
			priq.push({ res[aa.to], aa.to });
		}
	}
	return res;
}


int main() {

	int n, m, s, t, k;
	scanf("%d%d%d%d%d", &n, &m, &s, &t, &k);
	if (n == 2) {
		if (m == 1) {
			printyn(k % 2 == 1);
		}
		else {
			if (k % 2 == 0)puts("No");
			else puts("Unknown");
		}
		Please AC;
	}
	--s, --t;
	graph<int> g(n, false, false);
	g.read(m, true);
	auto d = dijkstra(g, s, n, INF);
	if (d[t] == INF) {
		puts("Unknown");
	}
	else if (d[t] % 2 == k % 2 and d[t] <= k) {
		puts("Yes");
	}
	else if (d[t] % 2 == k % 2) {
		puts("Unknown");
	}
	else {
		puts("No");
	}

	Please AC;
}