#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int n, m;
    cin >> n >> m;
    int s, t, k;
    cin >> s >> t >> k;
    --s;--t;
    vector<vector<int>> g(n);
    rep(i,m){
        int a, b;
        cin >> a >> b;
        --a;--b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    const int INF = 1e9;
    vector<int> dist(n, INF);
    dist[s] = 0;
    queue<int> q;
    q.push(s);
    vector<int> col(n);
    col[0]=1;
    while(!q.empty()) {
        int u = q.front();q.pop();
        for(int v : g[u]) {
            if(dist[v]!=INF) continue;
            dist[v] = dist[u] + 1;
            col[v]=col[u]^1;
            q.push(v);
        }
    }
    dbg(dist);
    if(n==1){
        cout<<"No"<<endl;
        return 0;
    }
    if(n==2 && s==t && m==0){
        if(k%2==1){
            cout<<"No"<<endl;
        }
        else{
            cout<<"Unknown"<<endl;
        }
        return 0;
    }
    if(dist[t]==INF) {
        if(n==2 && k%2==0) {
            cout<<"No"<<endl;
        }
        else{
            cout<<"Unknown"<<endl;
        }
        return 0;
    }
    if(abs(dist[t]-k)%2==1){
        cout<<"No"<<endl;
        return 0;
    }
    if(dist[t]<=k) {
        cout<<"Yes"<<endl;
        return 0;
    }
    if(col[t]!=col[s]){
        
    }
    cout<<"Unknown"<<endl;
    return 0;
}