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

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

void dfs(long long now, long long sta, long long col)
{
    if(visited[now]) return;
    visited[now] = true;
    color[now] = {sta,col};
    for(long long nxt:e[now])
    {
        dfs(nxt, sta, col^1);
    }
}

int main()
{
    cin >> n >> m >> s >> t >> k;
    for(long long i=0;i<m;i++)
    {
        cin >> a >> b;
        a--;b--;
        e[a].push_back(b);
        e[b].push_back(a);
    }
    for(long long i=0;i<n;i++)
    {
        dfs(i, i, 0);
    }
    s--;t--;
    if(color[s].first==color[t].first)
    {
        long long bi1 = color[s].second;
        long long bi2 = color[t].second;
        if(k%2 == bi1^bi2)
        {
            long long dst;
            //到達できるか?
            queue<pair<long long,long long>>idx_len;
            idx_len.push({s,0});
            while(!idx_len.empty())
            {
                auto [idx, len] = idx_len.front();
                idx_len.pop();

                if(length[idx]) continue;
                length[idx] = true;

                if(idx==t) dst = len;
                for(long long nxt:e[idx])
                {
                    idx_len.push({nxt, len+1});
                }
            }
            if(dst<=k)
            {
                cout << "Yes" << endl;
            }
            else
            {
                cout << "Unknown" << endl;
            }
        }
        else
        {
            cout << "No" << endl;
        }
    }
    else
    {
        cout << "Unknown" << endl;
    }
}