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

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

#define rep(i,n) for(int i = 0; i < (int)n; i++)
#define FOR(n) for(int i = 0; i < (int)n; i++)
#define repi(i,a,b) for(int i = (int)a; i < (int)b; i++)
#define all(x) x.begin(),x.end()
//#define mp make_pair
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vvvvi vector<vvvi>
#define pii pair<int,int>
#define vpii vector<pair<int,int>>

template<typename T>
bool chmax(T &a, const T b) {if(a<b) {a=b; return true;} else {return false;}}
template<typename T>
bool chmin(T &a, const T b) {if(a>b) {a=b; return true;} else {return false;}}

using ll = long long;
using ld = long double;
using ull = unsigned long long;

const ll INF = numeric_limits<long long>::max() / 2;
const ld pi = 3.1415926535897932384626433832795028;
const ll mod = 998244353;
int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

#define int long long

struct Is_Bipartite {
    int n;
    vector<int> color;
    vector<vector<int>> g;

    Is_Bipartite(int n) : n(n), g(n) {}
    Is_Bipartite(vector<vector<int>> g) : n(g.size()), g(g) {}

    void add_edge(int a, int b) {
        g[a].push_back(b);
        g[b].push_back(a);
    }

    bool dfs(int v, int col) {
        color[v] = col;

        for(auto e : g[v]) {
            if(color[e] == col) {
                return false;
            }
            if(color[e] == -1) {
                if(!dfs(e, 1-col)) return false;
            }
        }
        
        return true;
    }

    vi generate(int st) {
        color.assign(n, -1);
        dfs(st, 0);
        return color;
    }
};

vector<int> bfs(vector<vector<int>> &g, int s) {
    int n = g.size();
    queue<int> que;
    vi dist(n, -1);
    que.push(s);
    dist[s] = 0;
    while(!que.empty()) {
        int v = que.front();
        que.pop();
        for(auto e : g[v]) {
            if(dist[e] < 0) {
                dist[e] = dist[v] + 1;
                que.push(e);
            }
        }
    }
    return dist;
}

void solve() {
    int n, m;
    cin >> n >> m;
    int s, t, k;
    cin >> s >> t >> k;
    --s;
    --t;
    Is_Bipartite g(n);
    vvi bg(n);
    FOR(m) {
        int a, b;
        cin >> a >> b;
        --a;
        --b;
        g.add_edge(a, b);
        bg[a].push_back(b);
        bg[b].push_back(a);
    }
    vi color = g.generate(s);
    vi dist = bfs(bg, s);
    if(color[t] == -1) cout << "Unknown" << endl;
    else if(abs(color[t]-color[s])%2 == k%2) {
        if(dist[t] <= k) cout << "Yes" << endl;
        else cout << "Unknown" << endl;
    }else cout << "No" << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}