/* -*- coding: utf-8 -*-
 *
 * 2674.cc:  No.2674 k-Walk on Bipartite - yukicoder
 */

#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef vector<int> vi;
typedef queue<int> qi;

/* global variables */

vi nbrs[MAX_N];
int ds[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, m, s, t, k;
  scanf("%d%d%d%d%d", &n, &m, &s, &t, &k);
  s--, t--;

  for (int i = 0; i < m; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u--, v--;
    nbrs[u].push_back(v);
    nbrs[v].push_back(u);
  }

  fill(ds, ds + n, -1);
  ds[s] = 0;
  qi q;
  q.push(s);
  int sz = 1;

  while (! q.empty()) {
    int u = q.front(); q.pop();
    for (auto v: nbrs[u])
      if (ds[v] < 0) {
	ds[v] = ds[u] + 1, sz++;
	q.push(v);
      }
  }

  if (ds[t] >= 0) {
    if ((k - ds[t]) & 1) puts("No");
    else if (s == t) {
      if (sz > 1) puts("Yes");
      else if (n == 1) puts("No");
      else puts("Unknown");
    }
    else {
      if (s != t && ds[t] <= k) puts("Yes");
      else puts("Unknown");
    }
  }
  else {
    if (n == 2 && ! (k & 1)) puts("No");
    else puts("Unknown");
  }

  return 0;
}