#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2")
#include <bits/stdc++.h>
#define INF 1000000001LL
#define LNF 1000000000000000001LL
#define MOD 1000000007LL
#define MAX 200001
#define long long long
#define all(x) x.begin(),x.end()
using namespace std;

vector<int> graph[MAX];
int main()
{
	ios_base::sync_with_stdio(0); 
    cin.tie(0);

    int n,m;
    cin >> n >> m;
    int s,e,k;
    cin >> s >> e >> k;

    for(int i = 0; i<m; i++)
    {
        int a,b;
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    
    vector<int> vis(n+1,-1);
    queue<int> q;
    q.push(s);
    while(!q.empty())
    {
        int x = q.front();
        q.pop();

        for(int y : graph[x])
        {
            if(vis[y] == -1)
            {
                vis[y] = vis[x]+1;
                q.push(y);
            }
        }
    }

    if(n == 1)
    {
        cout << "No\n";
        return 0;
    }

    if(vis[e] <= k)
    {
        if(vis[e] == -1)
        {
            if(n == 2 && k%2)
            {
                cout << "Unknown\n";
            }
            else if(n == 2)
            {
                cout << "No\n";
            }
            else
                cout << "Unknown\n";
        } 
        else if(vis[e]%2 == k%2)
            cout << "Yes\n";
        else
            cout << "No\n";
    }
    else
    {
        if(vis[e]%2 == k%2)
            cout << "Unknown\n";
        else
            cout << "No\n";
    }
    return 0;
}