#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);
	UnionFind uf(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);
		uf.unite(u,v);
	}
	if(uf.same(s,t))
	{
		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);
				}
			}
		};
		dfs(dfs,s,0);
		if(C[s] == C[t] && k % 2 == 1)
		{
			cout << "No\n";
			return;
		}
		if(C[s] != C[t] && k % 2 == 0)
		{
			cout << "No\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);
				}
			}
		}
		if(dp[t] <= k)
		{
			cout << "Yes\n";
		}
		else
		{
			cout << "Unknown\n";
		}
	}
	else
	{
		cout << "Unknown\n";
	}
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int tt = 1;
	/* cin >> tt; */
	while(tt--) Main();
}