#include <bits/stdc++.h>

using namespace std;
using ll = long long;

struct UnionFind {
    int ngroup, N;
    vector<int> par, siz;

    UnionFind(int _N) : N(_N), par(_N), siz(_N){
        ngroup = _N;
        for(int i = 0; i < N; i++) par[i] = i, siz[i] = 1;
    }

    int root(int x) {
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    int unite(int x, int y) {
        int rx = root(x), ry = root(y);
        if (rx == ry) return rx;
        ngroup--;
        if (siz[rx] > siz[ry]) swap(rx, ry);
        par[rx] = ry; siz[ry] += siz[rx];
        return ry;
    }

    bool same(int x, int y) {
        int rx = root(x), ry = root(y);
        return rx == ry;
    }

    int size(int x) {return siz[root(x)];}
    int group_count() {return ngroup;}

    vector<vector<int>> groups(){
        vector<int> rev(N); int nrt=0;
        for (int i=0; i<N; i++) if (root(i) == i) rev[i] = nrt, nrt++;
        vector<vector<int>> res(nrt);
        for (int i=0; i<N; i++) res[rev[root(i)]].push_back(i);

        return res;
    }
};

vector<int> bfs(vector<vector<int>> &E, int start){

    int N = E.size();
    int from, to;
    queue<int> que;
    vector<int> dist(N, 1e9);

    dist[start] = 0;
    que.push(start);

    while(!que.empty()){
        from = que.front();
        que.pop();
        for (auto to : E[from]){
            if (dist[to] != 1e9) continue;
            dist[to] = dist[from] + 1;
            que.push(to);
        }
    }

    return dist;
}

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    int N, M, s, t, k, a, b;
    cin >> N >> M >> s >> t >> k;

    auto YES = [](){cout << "Yes" << endl; exit(0);};
    auto NO = [](){cout << "No" << endl; exit(0);};
    auto UNKNOWN = [](){cout << "Unknown" << endl; exit(0);};

    vector<vector<int>> E(N+1);
    UnionFind uf(N+1);

    for (int i=1; i<=M; i++){
        cin >> a >> b;
        E[a].push_back(b);
        E[b].push_back(a);
        uf.unite(a, b);
    }

    if (!uf.same(s, t)){
        if (k % 2 == 1) UNKNOWN();
        if (uf.size(s) >= 2 || uf.size(t) >= 2) UNKNOWN();
        if (N > 2) UNKNOWN();
        NO();
    }

    if (s == t && M == 0){
        if (N == 1) NO();
        if (k % 2 == 1) NO();
        UNKNOWN(); 
    }

    vector<int> color(N+1, -1);

    auto dfs=[&](auto self, int from)->void{
        for (auto to : E[from]){
            if (color[to] != -1) continue;
            color[to] = 1 - color[from];
            self(self, to);
        }
    };

    color[s] = 0;

    dfs(dfs, s);

    if (abs(color[s]-color[t]) % 2 != k % 2) NO();
    vector<int> dist = bfs(E, s);

    if (dist[t] <= k) YES();
    else UNKNOWN();

    return 0;
}