// An AC a day keeps the doctor away.
#include <bits/stdc++.h>
using namespace std;

/*{{{*/
#define all(x) begin(x), end(x)
#ifdef CKISEKI
#include <experimental/iterator>
#define safe cerr<<__PRETTY_FUNCTION__<<" line "<<__LINE__<<" safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
void debug_(auto s, auto ...a) {
  cerr << "\e[1;32m(" << s << ") = (";
  int f = 0;
  (..., (cerr << (f++ ? ", " : "") << a));
  cerr << ")\e[0m\n";
}
void orange_(auto s, auto L, auto R) {
  cerr << "\e[1;33m[ " << s << " ] = [ ";
  using namespace experimental;
  copy(L, R, make_ostream_joiner(cerr, ", "));
  cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

template <typename T, T MOD> class Modular {
  public:
    constexpr Modular() : v() {}
    template <typename U> Modular(const U &u) { v = (0 <= u && u < MOD ? u : (u%MOD+MOD)%MOD); }
    template <typename U> explicit operator U() const { return U(v); }
    T operator()() const { return v; }
#define REFOP(type, expr...) Modular &operator type (const Modular &rhs) { return expr, *this; }
    REFOP(+=, v += rhs.v - MOD, v += MOD & (v >> width)) ; REFOP(-=, v -= rhs.v, v += MOD & (v >> width))
    // fits for MOD^2 <= 9e18
    REFOP(*=, v = static_cast<T>(1LL * v * rhs.v % MOD)) ; REFOP(/=, *this *= inverse(rhs.v))
#define VALOP(op) friend Modular operator op (Modular a, const Modular &b) { return a op##= b; }
    VALOP(+) ; VALOP(-) ; VALOP(*) ; VALOP(/)
    Modular operator-() const { return 0 - *this; }
    friend bool operator == (const Modular &lhs, const Modular &rhs) { return lhs.v == rhs.v; }
    friend bool operator != (const Modular &lhs, const Modular &rhs) { return lhs.v != rhs.v; }
    friend std::istream & operator>>(std::istream &I, Modular &m) { T x; I >> x, m = x; return I; }
    friend std::ostream & operator<<(std::ostream &O, const Modular &m) { return O << m.v; }
  private:
    constexpr static int width = sizeof(T) * 8 - 1;
    T v;
    static T inverse(T a) {
      // copy from tourist's template
      T u = 0, v = 1, m = MOD;
      while (a != 0) {
        T t = m / a;
        m -= t * a; std::swap(a, m);
        u -= t * v; std::swap(u, v);
      }
      assert(m == 1);
      return u;
    }
};

using lld = int64_t;
using llf = long double;
template <typename T> using max_heap = std::priority_queue<T,vector<T>,less<T> >;
template <typename T> using min_heap = std::priority_queue<T,vector<T>,greater<T> >;
template <typename V, typename T> int get_pos(const V &v, T x) { return lower_bound(all(v),x) - begin(v); }
template <typename V> void sort_uni(V &v) { sort(all(v)), v.erase(unique(all(v)),end(v)); }
template <typename T> bool chmin(T &x, const T &v) { return v < x ? (x=v, true) : false; }
template <typename T> bool chmax(T &x, const T &v) { return x < v ? (x=v, true) : false; }
constexpr inline lld cdiv(lld x, lld m) { return x/m + (x%m ? (x<0) ^ (m>0) : 0); } // ceiling divide
constexpr inline lld modpow(lld e,lld p,lld m) { lld r=1; for(e%=m;p;p>>=1,e=e*e%m) if(p&1) r=r*e%m; return r; }/*}}}*/

constexpr llf eps = 1e-9;
constexpr lld maxn = 200025, INF = 1e18, mod = 998244353, K = 14699, inf = 1e9;
using Mint = Modular<int, mod>;
Mint modpow(Mint e, uint64_t p) { Mint r = 1; while (p) (p&1) && (r *= e), e *= e, p >>= 1; return r; } // 0^0 = 1

const auto dummy = [] { return cin.tie(nullptr)->sync_with_stdio(false); }();

signed main() {
  int N, M, S, T, K;
  cin >> N >> M >> S >> T >> K;
  --S, --T;
  vector<vector<int>> g(N);

  for (int i = 0; i < M; i++) {
    int a, b;
    cin >> a >> b;
    --a, --b;
    g[a].emplace_back(b);
    g[b].emplace_back(a);
  }

  if (S == T) {
    if (K % 2 == 1)
      return cout << "No\n", 0;
    if (g[S].size())
      return cout << "Yes\n", 0;
    if (N == 1)
      return cout << "No\n", 0;
    cout << "Unknown\n";
    return 0;
  }

  queue<int> q;
  vector<int> dis(N, -1);
  q.push(S);
  dis[S] = 0;

  while (!q.empty()) {
    int i = q.front(); q.pop();
    for (int j : g[i]) {
      if (dis[j] == -1) {
        dis[j] = dis[i] + 1;
        q.push(j);
      }
    }
  }

  debug(dis[T], K);
  if (dis[T] != -1 && dis[T] % 2 != K % 2)
    return cout << "No\n", 0;
  if (dis[T] != -1 && dis[T] <= K)
    return cout << "Yes\n", 0;
  cout << "Unknown\n";
}