#include <bits/stdc++.h>

using namespace std;

#define overload4(_1, _2, _3, _4, name, ...) name
#define rep1(n) for(int i = 0; i < (int)(n); ++i)
#define rep2(i, n) for(int i = 0; i < (int)(n); ++i)
#define rep3(i, a, b) for(int i = (a); i < (int)(b); ++i)
#define rep4(i, a, b, c) for(int i = (a); i < (int)(b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)

#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; --i)
#define ALL(a) (a).begin(), (a).end()
#define Sort(a) (sort((a).begin(), (a).end()))
#define RSort(a) (sort((a).rbegin(), (a).rend()))
#define UNIQUE(a) (a.erase(unique((a).begin(), (a).end()), (a).end()))

typedef long long int ll;
typedef unsigned long long ul;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<char> vc;
typedef vector<string> vst;
typedef vector<double> vd;
typedef vector<long double> vld;
typedef pair<long long, long long> P;

template<class T> long long sum(const T& a){ return accumulate(a.begin(), a.end(), 0LL); }
template<class T> auto min(const T& a){ return *min_element(a.begin(), a.end()); }
template<class T> auto max(const T& a){ return *max_element(a.begin(), a.end()); }

const long long MINF = 0x7fffffffffff;
const long long INF = 0x1fffffffffffffff;
const long long MOD = 998244353;
const long double EPS = 1e-9;
const long double PI = acos(-1);
 
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p){ is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){ os << "(" << p.first << ", " << p.second << ")"; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for(T &in : v) is >> in; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v){ for(int i = 0; i < (int) v.size(); ++i){ os << v[i] << (i + 1 != (int) v.size() ? " " : ""); } return os; }
template <typename T, typename S> ostream &operator<<(ostream &os, const map<T, S> &mp){ for(auto &[key, val] : mp){ os << key << ":" << val << " "; } return os; }
template <typename T> ostream &operator<<(ostream &os, const set<T> &st){ auto itr = st.begin(); for(int i = 0; i < (int)st.size(); ++i){ os << *itr << (i + 1 != (int)st.size() ? " " : ""); itr++; } return os; }
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &st){ auto itr = st.begin(); for(int i = 0; i < (int)st.size(); ++i){ os << *itr << (i + 1 != (int)st.size() ? " " : ""); itr++; } return os; }
template <typename T> ostream &operator<<(ostream &os, queue<T> q){ while(q.size()){ os << q.front() << " "; q.pop(); } return os; }
template <typename T> ostream &operator<<(ostream &os, deque<T> q){ while(q.size()){ os << q.front() << " "; q.pop_front(); } return os; }
template <typename T> ostream &operator<<(ostream &os, stack<T> st){ while(st.size()){ os << st.top() << " "; st.pop(); } return os; }
template <class T, class Container, class Compare> ostream &operator<<(ostream &os, priority_queue<T, Container, Compare> pq){ while(pq.size()){ os << pq.top() << " "; pq.pop(); } return os; }

template<class T, class U> inline T vin(T& vec, U n) { vec.resize(n); for(int i = 0; i < (int) n; ++i) cin >> vec[i]; return vec; }
template<class T> inline void vout(T vec, string s = "\n"){ for(auto x : vec) cout << x << s; }
template<class... T> void in(T&... a){ (cin >> ... >> a); }
void out(){ cout << '\n'; }
template<class T, class... Ts> void out(const T& a, const Ts&... b){ cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; }
template<class T, class U> void inGraph(vector<vector<T>>& G, U n, U m, bool directed = false){ G.resize(n); for(int i = 0; i < m; ++i){ int a, b; cin >> a >> b; a--, b--; G[a].push_back(b); if(!directed) G[b].push_back(a); } }

template <typename T>
vector<long long> dijkstra(const vector<vector<array<long long, 2>>> &G, T x){
    const long long INF = 0x1fffffffffffffff;
    vector<long long> cost((int) G.size(), INF);
    using P = pair<long long, long long>;
    priority_queue<P, vector<P>, greater<>> q;
    cost[x] = 0;
    q.emplace(0, x);
    
    while(q.size()){
        auto [c, at] = q.top();
        q.pop();
        if(c > cost[at]) continue;
        for(auto& [to, t] : G[at]){
            if(cost[to] > c + t){
                cost[to] = c + t;
                q.emplace(cost[to], to);
            }
        }
    }
    return cost;
}

ll n, m, s, t, k;
vll a, b;

void input(){
    in(n, m, s, t, k);
    a.resize(m);
    b.resize(m);
    rep(i, m) in(a[i], b[i]);
}

void solve(){
    s--, t--;
    if(n == 1){
        out("No");
        return;
    }else if(n == 2){
        if(s == t && k % 2 == 0){
            if(m == 0) out("Unknown");
            else out("Yes");
        }else if(s != t && k % 2 == 1){
            if(m == 0) out("Unknown");
            else out("Yes");
        }else{
            out("No");
        }
        return;
    }

    vector<vector<array<ll, 2>>> G(n);
    vll color(n, -1), check(n);
    rep(i, m){
    	a[i]--, b[i]--;
        G[a[i]].push_back({b[i], 1});
        G[b[i]].push_back({a[i], 1});
    }
    auto dfs = [&](auto &self, ll curr, ll prev) -> void {
        if(prev == -1){
            color[curr] = 0;
        }else{
            color[curr] = color[prev] ^ 1;
        }
        check[curr] = 1;
        for(auto [x, w] : G[curr]){
            if(check[x]) continue;
            self(self, x, curr);
        }
        return;
    };
    dfs(dfs, s, -1);
    if(color[t] == -1){
        out("Unknown");
        return;
    }
    if(color[s] == color[t] && k % 2){
        out("No");
        return;
    }
    if(color[s] != color[t] && k % 2 == 0){
        out("No");
        return;
    }
    vll cost = dijkstra(G, s);
    if(cost[t] <= k){
        out("Yes");
    }else{
    	out("Unknown");
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(20);
    
    input();
    solve();
}