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

#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

// using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

int main() {
    ll N, M;
    cin >> N >> M;
    ll s, t, k;
    cin >> s >> t >> k;
    s--;
    t--;
    vector<ll> A(M);
    vector<ll> B(M);
    for (ll i = 0; i < M; i++) {
        cin >> A[i] >> B[i];
        A[i]--;
        B[i]--;
    }
    vector<vector<ll>> graph(N, vector<ll>(0));
    for (ll i = 0; i < M; i++) {
        graph[A[i]].push_back(B[i]);
        graph[B[i]].push_back(A[i]);
    }
    dsu tree(N);
    for (ll i = 0; i < M; i++) {
        tree.merge(A[i], B[i]);
    }
    if (!tree.same(s, t)) {
        cout << "Unknown" << endl;
    } else {
        ll INF = 100000000024;
        vector<ll> dist(N, INF);
        vector<ll> color(N, -1);
        queue<ll> que;
        dist[s] = 0;
        color[s] = 0;
        que.push(s);
        while (que.size()) {
            ll p = que.front();
            que.pop();
            for (ll x : graph[p]) {
                if (dist[x] == INF) {
                    color[x] = 1 - color[p];
                    dist[x] = dist[p] + 1;
                    que.push(x);
                }
            }
        }
        if (k % 2 != dist[t] % 2) {
            cout << "No" << endl;
        } else {
            if (s == t) {
                if (graph[s].size() == 0) {
                    cout << "Unknown" << endl;
                } else {
                    cout << "Yes" << endl;
                }
            } else {
                if (dist[t] <= k) {
                    cout << "Yes" << endl;
                } else {
                    cout << "Unknown" << endl;
                }
            }
        }
    }
}