#include <atcoder/all>
#include <bits/stdc++.h>

using namespace std;
using namespace atcoder;

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using P = pair<ll, ll>;
using tp = tuple<ll, ll, ll>;

template <class T>
using vec = vector<T>;
template <class T>
using vvec = vector<vec<T>>;

#define all(hoge) (hoge).begin(), (hoge).end()
#define en '\n'
#define rep(i, m, n) for(ll i = (ll)(m); i < (ll)(n); ++i)
#define rep2(i, m, n) for(ll i = (ll)(n)-1; i >= (ll)(m); --i)
#define REP(i, n) rep(i, 0, n)
#define REP2(i, n) rep2(i, 0, n)

constexpr long long INF = 1LL << 60;
constexpr int INF_INT = 1 << 25;
// constexpr long long MOD = (ll)1e9 + 7;
constexpr long long MOD = 998244353LL;
static const ld pi = 3.141592653589793L;

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

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;
}

struct Edge {
    int to, rev;
    ll cap;
    Edge(int _to, int _rev, ll _cap) : to(_to), rev(_rev), cap(_cap) {}
};

typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

void add_edge(Graph &G, int from, int to, ll cap, bool revFlag, ll revCap) {
    G[from].push_back(Edge(to, (int)G[to].size(), cap));
    if(revFlag)
        G[to].push_back(Edge(from, (int)G[from].size() - 1, revCap));
}

void Dijkstra(Graph &g, ll s, vec<ll> &d) { // O(|E|log|V|)
    d.resize(g.size());
    REP(i, d.size())
    d[i] = INF;
    d[s] = 0;
    priority_queue<P, vector<P>, greater<P>> q;
    q.push({0, s});
    while(!q.empty()) {
        auto [dd, v] = q.top();
        q.pop();
        if(d[v] < dd)
            continue;
        for(auto &e : g[v]) {
            if(d[e.to] > dd + e.cap) {
                d[e.to] = dd + e.cap;
                q.push({d[e.to], e.to});
            }
        }
    }
}

void solve() {
    int n, m;
    cin >> n >> m;
    int s, t, k;
    cin >> s >> t >> k;
    s--;
    t--;
    Graph g(n);
    REP(i, m) {
        int u, v;
        cin >> u >> v;
        u--;
        v--;
        add_edge(g, u, v, 1, true, 1);
    }

    vec<ll> d;
    Dijkstra(g, s, d);
    if(d[t] == INF or d[t] > k) {
        cout << "Unknown" << en;
    } else if(d[t] % 2 == k % 2) {
        cout << "Yes" << en;
    } else {
        cout << "No" << en;
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    // cout << fixed << setprecision(10);

    // ll t;
    // cin >> t;
    // REP(i, t - 1) {
    //     solve();
    // }

    solve();

    return 0;
}