#include<bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("Ofast")

#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a >= b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

int main(){
    ll n,m,s,t,k;cin >> n >> m >> s >> t >> k;s--;t--;
    vvl g(n);
    rep(i,m){
        ll a,b;cin >> a >> b;a--;b--;
        g[a].emplace_back(b);
        g[b].emplace_back(a);
    }
    {
        if(n==1){
            cout << "No" << endl;
            return 0;
        }
    }
    {
        if(n==2){
            vl mle(INF);
            if(m==0){
                if(s!=t){
                    if(k%2==0){
                        cout << "No" << endl;
                        return 0;
                    }
                    else{
                        cout << "Unknown" << endl;
                        return 0;
                    }
                }
            }
        }
    }
    vl dist(n,INF);
    queue<ll> que;
    dist[s]=0;
    que.push(s);
    while(que.size()){
        ll v=que.front();que.pop();
        for(auto p:g[v]){
            if(dist[p]!=INF)continue;
            dist[p]=dist[v]+1;
            que.push(p);
        }
    }
    if(dist[t]==INF){
        cout << "Unknown" << endl;
    }
    else{
        if(k%2!=dist[t]%2){
            cout << "No" << endl;
        }
        else if(k>=dist[t]){
            cout << "Yes" << endl;
        }
        else cout << "Unknown" << endl;
    }
}