#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


template<typename T>
struct edge{
    int from, to;
    T cost;
    int id;

    edge(){}
    edge(int to, T cost=1) : from(-1), to(to), cost(cost){}
    edge(int to, T cost, int id) : from(-1), to(to), cost(cost), id(id){}
    edge(int from, int to, T cost, int id) : from(from), to(to), cost(cost), id(id){}
};

template<typename T>
struct redge{
    int from, to;
    T cap, cost;
    int rev;
    
    redge(int to, T cap, T cost=(T)(1)) : from(-1), to(to), cap(cap), cost(cost){}
    redge(int to, T cap, T cost, int rev) : from(-1), to(to), cap(cap), cost(cost), rev(rev){}
};

template<typename T> using Edges = vector<edge<T>>;
template<typename T> using weighted_graph = vector<Edges<T>>;
template<typename T> using tree = vector<Edges<T>>;
using unweighted_graph = vector<vector<int>>;
template<typename T> using residual_graph = vector<vector<redge<T>>>;


vector<long long> dijkstra(weighted_graph<long long> G, int src){
    int n = (int)G.size();

    vector<long long> dist(n, LINF);
    dist[src] = 0;
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> PQ;
    PQ.push({0, src});
    while(!PQ.empty()){
        int v = PQ.top().second;
        long long tmp = PQ.top().first;
        PQ.pop();
        if(dist[v] < tmp) continue;

        for(edge<long long> e : G[v]){
            if(dist[v]+e.cost < dist[e.to]){
                dist[e.to] = dist[v]+e.cost;
                PQ.push({dist[e.to], e.to});
            }
        }
    }

    return dist;
}


struct union_find{
    vector<int> par;
    vector<int> siz;
    
    union_find(int n) : par(n), siz(n, 1){
        for(int i=0; i<n; i++) par[i] = i;
    }
    
    int root(int x){
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }
 
    void unite(int x, int y){
        int rx = root(x);
        int ry = root(y);
        if (rx == ry) return;
        if (siz[rx] < siz[ry]) swap(rx, ry);
        siz[rx] += siz[ry];
        par[ry] = rx;
    }
 
    bool same(int x, int y){
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }
 
    int size(int x){
        return siz[root(x)];
    }
};


void solve(){
    int n, m; cin >> n >> m;
    int s, t, k; cin >> s >> t >> k;
    s--; t--;
    weighted_graph<ll> G(n);
    union_find uf(n);
    for(int i=0; i<m; i++){
        int u, v; cin >> u >> v;
        u--; v--;
        G[u].pb(edge<ll>(v));
        G[v].pb(edge<ll>(u));
        uf.unite(u, v);
    }

    if(s==t){
        if(k%2==1){
            cout << "No\n";
        }else{
            if(uf.size(s)>=2){
                cout << "Yes\n";
            }else{
                if(n==1){
                    cout << "No\n";
                }else if(n>=2){
                    cout << "Unknown\n";
                }
            }
        }

        return;
    }

    if(!uf.same(s, t)){
        if(n>=3){
            cout << "Unknown\n";
        }else if(n==2){
            if(k%2==1){
                cout << "Unknown\n";
            }else{
                cout << "No\n";
            }
        }else if(n==1){
            cout << "No\n";
        }

        return;
    }

    vector<ll> dist = dijkstra(G, s);
    if(dist[t]%2 != k%2){
        cout << "No\n";
    }else{
        if(dist[t]<=k){
            cout << "Yes\n";
        }else{
            cout << "Unknown\n";
        }
    }
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}