#include using namespace std; //#pragma GCC optimize("Ofast") #define rep(i,n) for(ll i=0;i=0;i--) #define perl(i,r,l) for(ll i=r-1;i>=l;i--) #define fi first #define se second #define pb push_back #define ins insert #define pqueue(x) priority_queue,greater> #define all(x) (x).begin(),(x).end() #define CST(x) cout<> #define rev(x) reverse(x); using ll=long long; using vl=vector; using vvl=vector>; using pl=pair; using vpl=vector; using vvpl=vector; const ll MOD=1000000007; const ll MOD9=998244353; const int inf=1e9+10; const ll INF=4e18; const ll dy[9]={1,0,-1,0,1,1,-1,-1,0}; const ll dx[9]={0,1,0,-1,1,-1,1,-1,0}; template inline bool chmin(T& a, T b) { if (a >= b) { a = b; return true; } return false; } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; } int main(){ ll n,m,s,t,k;cin >> n >> m >> s >> t >> k;s--;t--; vvl g(n); rep(i,m){ ll a,b;cin >> a >> b;a--;b--; g[a].emplace_back(b); g[b].emplace_back(a); } { if(n==1){ cout << "No" << endl; return 0; } } { if(n==2){ vl mle(INF); if(m==0){ if(s!=t){ if(k%2==0){ cout << "No" << endl; return 0; } else{ cout << "Unknown" << endl; return 0; } } } } } vl dist(n,INF); queue que; dist[s]=0; que.push(s); while(que.size()){ ll v=que.front();que.pop(); for(auto p:g[v]){ if(dist[p]!=INF)continue; dist[p]=dist[v]+1; que.push(p); } } if(dist[t]==INF){ cout << "Unknown" << endl; } else{ if(k%2!=dist[t]%2){ cout << "No" << endl; } else if(k>=dist[t]){ cout << "Yes" << endl; } else cout << "Unknown" << endl; } }