#include <atcoder/all>
#include <bits/stdc++.h>
using ll = long long;
using ull = unsigned long long;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); i++)
using namespace std;
using namespace atcoder;
using mint = modint998244353;
const int inf = 1000000007;
const ll longinf = 1ll << 60;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, m;
    cin >> n >> m;
    dsu uf(n * 2);
    int s, t, k;
    cin >> s >> t >> k;
    --s;
    --t;
    vector<vector<int>> g(n);
    rep(i, m) {
        int x, y;
        cin >> x >> y;
        --x;
        --y;
        uf.merge(x, y + n);
        uf.merge(x + n, y);
        g[x].push_back(y);
        g[y].push_back(x);
    }
    vector<int> dist(n, inf);
    dist[s] = 0;
    queue<int> q;
    q.push(s);
    while(q.size()) {
        int x = q.front();
        q.pop();
        for(auto to : g[x]) {
            if(dist[to] == inf) {
                dist[to] = dist[x] + 1;
                q.push(to);
            }
        }
    }
    if(uf.same(s, t)) {
        if(k % 2 == 1) {
            cout << "No" << endl;
        } else if(s == t) {
            if(g[s].size() > 0) {
                cout << "Yes" << endl;
            } else {
                cout << "Unknown" << endl;
            }
        } else if(dist[t] <= k) {
            cout << "Yes" << endl;
        } else {
            cout << "Unknown" << endl;
        }
    } else if(uf.same(s, t + n)) {
        if(k % 2 == 0) {
            cout << "No" << endl;
        } else if(dist[t] <= k) {
            cout << "Yes" << endl;
        } else {
            cout << "Unknown" << endl;
        }
    } else {
        if(n == 1) {
            cout << "No" << endl;
        } else if(n == 2) {
            if(k % 2 == 1) {
                cout << "Unknown" << endl;
            } else {
                cout << "No" << endl;
            }
        } else {
            cout << "Unknown" << endl;
        }
    }
    return 0;
}