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

int N, M;
int S, T, K;
vector<int> G[202020];
int dist(){
    vector<int> D(N, -1);
    D[S] = 0;
    queue<int> que;
    que.push(S);
    while(que.size()){
        int v = que.front(); que.pop();
        for(int nv : G[v])if(D[nv] == -1){
            D[nv] = D[v] + 1;
            que.push(nv);
        }
    }
    return D[T];
}
int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> N >> M >> S >> T >> K;
    S--, T--;
    for(int i = 0;i < M;i++){
        int a, b; cin >> a >> b;
        a--, b--;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    int d = dist();
    if(d == -1){
        if(K % 2 == 1){
            cout << "Unknown\n";
        }else if(N == 2){
            cout << "No\n";
        }else{
            cout << "Unknown\n";
        }
    }else if(d % 2 != K % 2){
        cout << "No\n";
    }else if(d > K){
        cout << "Unknown\n";
    }else{
        cout << "Yes\n";
    }
    return 0;
}