#include <bits/stdc++.h>
using namespace std;

int n, m, s, t, k;

vector<long long> dijkstra(vector<vector<pair<int, long long>>> &g, int x) {
    vector<long long> dist(n, 1000000000000000000);
    vector<bool> visit(n, false);
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> que;
    dist[x] = 0LL;
    que.push({dist[x], x});
    while (!que.empty()) {
        int v = que.top().second;
        que.pop();
        if (visit[v]) {
            continue;
        }
        visit[v] = true;
        for (auto p : g[v]) {
            int next_v = p.first;
            long long d = p.second;
            if (dist[next_v] > dist[v] + d) {
                dist[next_v] = dist[v] + d;
                que.push({dist[next_v], next_v});
            }
        }
    }
    return dist;
}

int main() {
    cin >> n >> m >> s >> t >> k;
    s--;
    t--;
    vector<vector<pair<int, long long>>> g(n);
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        a--;
        b--;
        g[a].push_back({b, 1LL});
        g[b].push_back({a, 1LL});
    }
    vector<long long> dist = dijkstra(g, s);
    if (abs(dist[t] - k) % 2 == 0) {
        if (dist[t] <= k) {
            cout << "Yes" << endl;
        } else {
            cout << "Unknown" << endl;
        }
    } else {
        cout << "No" << endl;
    }
}