#include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <random>
#include <time.h>
#include <map>
using namespace std;

int n,m,s,t,k,a,b;
vector<int>e[200000];
int length[200000];
bool visited[200000];

void dfs(int now, int len=0)
{
    if(visited[now]) return;
    visited[now]=true;
    length[now]=len;
    for(int nxt:e[now]) dfs(nxt, len+1);
}

int main()
{
    cin >> n >> m >> s >> t >> k;
    for(int i=0;i<m;i++)
    {
        cin >> a >> b;
        a--;b--;
        e[a].push_back(b);
        e[b].push_back(a);
    }
    s--;t--;
    dfs(s);
    if(visited[t])
    {
        if(length[t]%2!=k%2)
        {
            cout << "No" << endl;
        }
        else
        {
            if(length[t]<=k)
            {
                cout << "No" << endl;
            }
            else
            {
                cout << "Unknown" << endl;
            }
        }
    }
    else
    {
        cout << "Unknown" << endl;
    }
}