# include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
const double pi = acos(-1);
template<class T>constexpr T inf() { return ::std::numeric_limits<T>::max(); }
template<class T>constexpr T hinf() { return inf<T>() / 2; }
template <typename T_char>T_char TL(T_char cX) { return tolower(cX); }
template <typename T_char>T_char TU(T_char cX) { return toupper(cX); }
template<class T> bool chmin(T& a,T b) { if(a > b){a = b; return true;} return false; }
template<class T> bool chmax(T& a,T b) { if(a < b){a = b; return true;} return false; }
template<class T> bool is_sqare(T a) { if(floor(sqrt(a)) * floor(sqrt(a)) == a){ return true; }return false; }
int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; }
int d_sum(ll n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; }
int d_cnt(ll n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; }
ll gcd(ll a, ll b) { if (b == 0)return a; return gcd(b, a%b); };
ll lcm(ll a, ll b) { ll g = gcd(a, b); return a / g*b; };
template<class T> using dijk = priority_queue<T, vector<T>, greater<T>>;
# define all(qpqpq)           (qpqpq).begin(),(qpqpq).end()
# define UNIQUE(wpwpw)        (wpwpw).erase(unique(all((wpwpw))),(wpwpw).end())
# define LOWER(epepe)         transform(all((epepe)),(epepe).begin(),TL<char>)
# define UPPER(rprpr)         transform(all((rprpr)),(rprpr).begin(),TU<char>)
# define rep(i,upupu)         for(ll i = 0, i##_len = (upupu);(i) < (i##_len);(i)++)
# define reps(i,opopo)        for(ll i = 1, i##_len = (opopo);(i) <= (i##_len);(i)++)
# define len(x)                ((ll)(x).size())
# define bit(n)               (1LL << (n))
# define pb push_back
# define exists(c, e)         ((c).find(e) != (c).end())
#ifdef LOCAL
#  include "_debug_print.hpp"
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

struct INIT{
	INIT(){
		std::ios::sync_with_stdio(false);
		std::cin.tie(0);
		cout << fixed << setprecision(20);
	}
}INIT;

struct union_find {
	vector<int> par, rnk;

    union_find(size_t size){
        par.resize(size);
        rnk.resize(size, 0);
        for(int i = 0;i < (int)size;i++){
            par[i] = i;
        }
    }

    int root(int x){
        if(par[x] == x)return x;
        else return par[x] = root(par[x]);
    }

    bool is_root(int x){
        return root(x) == x;
    }

    void unite(int x, int y){
        x = root(x);
        y = root(y);
        if(x == y)return;
        if(rnk[x] < rnk[y]){
            par[x] = y;
        }else{
            par[y] = x;
            if(rnk[x] == rnk[y])rnk[x]++;
        }
    }
    bool same(int x,int y){
        return root(x) == root(y);
    }
};

void solve(){
	int n, m;
	cin >> n >> m;
	int s, t, k;
	cin >> s >> t >> k;
	s--, t--;
	union_find uf(n);
	vector<vector<int>> g(n);
	rep(i, m){
		int a, b;
		cin >> a >> b;
		a--, b--;
		uf.unite(a, b);
		g[a].pb(b);
		g[b].pb(a);
	}

	if(n == 1){
		cout << (k == 0 ? "Yes" : "No") << endl;
		return;
	}

	if(n == 2){
		if(s == t){
			if(uf.same(0, 1)){
				cout << (k%2 == 0 ? "Yes" : "No") << endl;
				return;
			}else{
				cout << (k%2 == 0 ? "Unknown" : "No") << endl;
			}
			return;
		}else{
			if(uf.same(0, 1)){
				cout << (k%2 ? "Yes" : "No") << endl;
				return;
			}else{
				cout << (k%2 ? "Unknown" : "No") << endl;
			}
			return;
		}
	}

	if(not uf.same(s, t)){
		cout << "Unknown" << endl;
		return;
	}

	vector<int> dis(n, hinf<int>());
	dis[s] = 0;
	queue<int> q;
	q.push(s);
	while(not q.empty()){
		auto cur = q.front();
		q.pop();
		for(auto to : g[cur]){
			if(dis[to] != hinf<int>())continue;
			dis[to] = dis[cur] + 1;
			q.push(to);
		}
	}

	if(dis[t]%2 != k%2){
		cout << "No" << endl;
		return;
	}

	cout << (dis[t] <= k ? "Yes" : "Unknown") << endl;
}

int main(){
    int t = 1;
    //cin >> t;
    while(t--)solve();
}