#include<bits/stdc++.h>
#include<atcoder/dsu>
using namespace std;
int N,M,s,t,K,dist[2<<17];
vector<int>G[2<<17];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>N>>M>>s>>t>>K;
    s--,t--;
    atcoder::dsu uf(N);
    for(;M--;)
    {
        int u,v;
        cin>>u>>v;
        u--,v--;
        G[u].push_back(v);
        G[v].push_back(u);
        uf.merge(u,v);
    }
    for(int i=0;i<N;i++)dist[i]=1<<30;
    dist[s]=0;
    queue<int>q;
    q.push(s);
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        for(int v:G[u])if(dist[v]>dist[u]+1)
        {
            dist[v]=dist[u]+1;
            q.push(v);
        }
    }
    if(dist[t]<=K&&(K-dist[t])%2==0)
    {
        cout<<"Yes\n";
        return 0;
    }
    if(uf.same(s,t))
    {
        assert(dist[t]<(1<<30));
        if((dist[t]-K)%2!=0)
        {
            cout<<"No\n";
            return 0;
        }
    }
    if(N==1)
    {
        cout<<"No\n";
        return 0;
    }
    if(N==2)
    {
        assert(!uf.same(0,1));
        if(K&1)
        {
            cout<<(s!=t?"Unknown\n":"No\n");
        }
        else
        {
            cout<<(s==t?"Unknown\n":"No\n");
        }
        return 0;
    }
    cout<<"Unknown\n";
}