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

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N,M;
int S,T,K;
vector<int> E[202020];
int D[202020];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>M;
	cin>>S>>T>>K;
	S--,T--;
	FOR(i,M) {
		cin>>x>>y;
		E[x-1].push_back(y-1);
		E[y-1].push_back(x-1);
	}
	
	FOR(i,N) D[i]=1<<20;
	D[S]=0;
	queue<int> Q;
	Q.push(S);
	while(Q.size()) {
		int cur=Q.front();
		Q.pop();
		FORR(e,E[cur]) if(D[e]==1<<20) {
			D[e]=D[cur]+1;
			Q.push(e);
		}
	}
	if(D[T]<1<<20) {
		assert(0);
		if(D[T]%2!=K%2) {
			cout<<"No"<<endl;
		}
		else if(D[T]<=K) {
			cout<<"Yes"<<endl;
		}
		else {
			cout<<"Unknown"<<endl;
		}
	}
	else if(K%2==0&&N==2) {
		cout<<"No"<<endl;
	}
	else {
		cout<<"Unknown"<<endl;
	}
		
	
	
	
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}