#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

int solve() {
  int n, m;
  cin >> n >> m;
  int s, t, k;
  cin >> s >> t >> k;
  s--, t--;
  VVI to(n);
  rep(_, m) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    to[a].emplace_back(b);
    to[b].emplace_back(a);
  }
  if (n == 1) return -1;
  VI dist(n, -1);
  dist[s] = 0;
  queue<int> q;
  q.emplace(s);
  while (q.size()) {
    int u = q.front(); q.pop();
    for (int v : to[u]) if (dist[v] == -1) {
      dist[v] = dist[u] + 1;
      q.emplace(v);
    }
  }
  if (s == t) {
    if (k % 2) return -1;
    if (to[s].empty()) return 0;
    return 1;
  }
  if (dist[t] == -1) {
    if (n == 2 && k % 2 == 0) return -1;
    return 0;
  }
  if (dist[t] % 2 != k % 2) return -1;
  if (dist[t] <= k) return 1;
  return 0;
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int res = solve();
  cout << (res == 1 ? "Yes\n" : res == 0 ? "Unknown\n" : "No\n");
}