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

class UnionFind{
    public:
    vector<int> par,siz;
 
    void make(int N){
        par.resize(N,-1);
        siz.resize(N,1);
    }
 
    int root(int x){
        if(par.at(x) == -1) return x;
        else return par.at(x) = root(par.at(x));
    }
 
    void unite(int u, int v){
        u = root(u),v = root(v);
        if(u == v) return;
        if(siz.at(u) < siz.at(v)) swap(u,v);
 
        par.at(v) = u;
        siz.at(u) += siz.at(v);
    }
 
    bool issame(int u, int v){
        if(root(u) == root(v)) return true;
        else return false;
    }
};

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

    int N,M; cin >> N >> M;
    int s,t,k; cin >> s >> t >> k;
    s--; t--;

    UnionFind Z; Z.make(N);
    vector<vector<int>> Graph(N);
    for(int i=0; i<M; i++){
        int u,v; cin >> u >> v;
        u--; v--;
        Z.unite(u,v);
        Graph.at(u).push_back(v);
        Graph.at(v).push_back(u);
    }
    if(Z.issame(s,t) == false){cout << "Unknown" << endl; return 0;}
    if(s == t){
        if(k%2) cout << "No" << endl;
        else if(Graph.at(s).size() == 0) cout << "Unknown" << endl;
        else cout << "Yes" << endl;
        return 0;
    }

    vector<int> color(N,-1),dist(N,-1);
    color.at(s) = 0; dist.at(s) = 0;
    queue<int> Q; Q.push(s);
    while(Q.size()){
        int pos = Q.front(); Q.pop();
        int d = dist.at(pos),c = color.at(pos);

        for(auto to : Graph.at(pos)){
            if(dist.at(to) != -1) continue;
            dist.at(to) = d+1; color.at(to) = c^1;
            Q.push(to);
        }
    }

    int diffc = 0;
    if(color.at(s) != color.at(t)) diffc = 1;
    if(k%2 != diffc) cout << "No" << endl;
    else if(dist.at(t) <= k) cout << "Yes" << endl;
    else cout << "Unknown" << endl;

}