#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <iterator>
#include <string>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <cassert>
#include <cmath>
#include <ctime>
#include <iomanip>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <bitset>
#include <random>
#include <utility>
#include <functional>
using namespace std;

#include<algorithm>
#include<vector>
#include<cassert>
using namespace std;
struct UnionFind
{
	private:
		int n;
		vector<int> par,siz;

	public:
		UnionFind(int n) :n(n),par(n,-1),siz(n,1) {}

		int root(int u) 
		{
			assert(0 <= u && u < n);
			return (par[u] < 0 ? u:par[u] = root(par[u]));
		}

		bool same(int u,int v)
		{
			assert(0 <= u && u < n && 0 <= v && v < n);
			return root(u) == root(v);
		}

		bool unite(int u,int v)
		{
			assert(0 <= u && u < n && 0 <= v && v < n);
			u = root(u),v = root(v);
			if(u == v) return false;

			if(siz[u] < siz[v]) swap(u,v);

			siz[u] += siz[v];
			par[v] = u;

			return true;
		}

		int size(int u)
		{
			assert(0 <= u && u < n);
			return siz[root(u)];
		}

		vector<vector<int>> components()
		{
			vector<vector<int>> ret(n);
			for(int u = 0;u < n;u++) ret[root(u)].push_back(u);

			ret.erase(remove_if(ret.begin(),ret.end(),[](vector<int> v) { return v.empty();}),ret.end());

			return ret;
		}
};

void Main()
{
	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 u,v;
		cin >> u >> v;
		u--; v--;
		G[u].push_back(v);
		G[v].push_back(u);
	}
	if(N == 1)
	{
		cout << "No\n";
		return;
	}
	/* if(N == 2) */
	/* { */
	/* 	if(s == t) */
	/* 	{ */
	/* 		if(M == 0) */
	/* 		{ */
	/* 			cout << "Unknown\n"; */
	/* 		} */
	/* 		else */
	/* 		{ */
	/* 			cout << (k % 2 == 0 ? "Yes\n" : "No\n"); */
	/* 		} */
	/* 	} */
	/* 	else */
	/* 	{ */
	/* 		if(k % 2 == 0) */
	/* 		{ */
	/* 			cout << "No\n"; */
	/* 		} */
	/* 		else */
	/* 		{ */
	/* 			cout << (M == 0 ? "Unknown\n" : "Yes\n"); */
	/* 		} */
	/* 	} */
	/* 	return; */
	/* } */
	vector<int> C(N,-1);
	auto dfs = [&](auto dfs,int u,int c) -> void
	{
		C[u] = c;
		for(int v : G[u])
		{
			if(C[v] == -1)
			{
				dfs(dfs,v,1 - c);
			}
			else
			{
				assert(C[v] == 1 - c);
			}
		}
	};
	dfs(dfs,s,0);
	if(C[t] == -1)
	{
		cout << "Unknown\n";
		return;
	}
	if(C[s] == C[t] && k % 2 == 1)
	{
		cout << "No\n";
		return;
	}
	if(C[s] != C[t] && k % 2 == 0)
	{
		cout << "No\n";
		return; 
	}
	int cnt = 0;
	for(int i = 0;i < N;i++)
	{
		if(C[i] != -1)
		{
			cnt++;
		}
	}
	if(cnt == 1)
	{
		cout << "Unknown\n";
		return;
	}
	vector<int> dp(N,-1);
	dp[s] = 0;
	queue<int> Q;
	Q.push(s);
	while(!Q.empty())
	{
		int u = Q.front();
		Q.pop();
		for(int v : G[u])
		{
			if(dp[v] == -1)
			{
				dp[v] = dp[u] + 1;
				Q.push(v);
			}
		}
	}
	assert(dp[t] % 2 == k % 2);
	if(dp[t] <= k)
	{
		cout << "Yes\n";
	}
	else
	{
		cout << "Unknown\n";
	}
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int tt = 1;
	/* cin >> tt; */
	while(tt--) Main();
}