import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }

string COLOR(string s = "") { return "\x1b[" ~ s ~ "m"; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


int root(int[] uf, int u) {
  return (uf[u] < 0) ? u : (uf[u] = uf.root(uf[u]));
}
bool connect(int[] uf, int u, int v) {
  u = uf.root(u);
  v = uf.root(v);
  if (u == v) return false;
  if (uf[u] > uf[v]) swap(u, v);
  uf[u] += uf[v];
  uf[v] = u;
  return true;
}


void main() {
  try {
    for (; ; ) {
      const N = readInt;
      const M = readInt;
      const S = readInt - 1;
      const T = readInt - 1;
      const K = readInt;
      auto A = new int[M];
      auto B = new int[M];
      foreach (i; 0 .. M) {
        A[i] = readInt - 1;
        B[i] = readInt - 1;
      }
      
      auto uf = new int[N << 1];
      uf[] = -1;
      foreach (i; 0 .. M) {
        uf.connect(A[i] << 1, B[i] << 1 | 1);
        uf.connect(B[i] << 1, A[i] << 1 | 1);
      }
      
      auto graph = new int[][N];
      foreach (i; 0 .. M) {
        graph[A[i]] ~= B[i];
        graph[B[i]] ~= A[i];
      }
      DList!int que;
      auto dist = new int[N];
      dist[] = -1;
      dist[S] = 0;
      que ~= cast(int)(S);
      for (; !que.empty; ) {
        const u = que.front;
        que.removeFront;
        foreach (v; graph[u]) {
          if (!~dist[v]) {
            dist[v] = dist[u] + 1;
            que ~= v;
          }
        }
      }
      debug {
        writeln("dist = ", dist);
      }
      
      int ans;
      if (N == 1) {
        ans = (K == 0) ? +1 : -1;
      } else {
        if (uf.root(S << 1) == uf.root(T << 1)) {
          assert(~dist[T]);
          assert(dist[T] % 2 == 0);
          ans = (K % 2 == 0) ? ((dist[T] <= K) ? +1 : 0) : -1;
        } else if (uf.root(S << 1) == uf.root(T << 1 | 1)) {
          assert(~dist[T]);
          assert(dist[T] % 2 != 0);
          ans = (K % 2 != 0) ? ((dist[T] <= K) ? +1 : 0) : -1;
        } else {
          assert(!~dist[T]);
          ans = 0;
        }
      }
      writeln(["No", "Unknown", "Yes"][1 + ans]);
    }
  } catch (EOFException e) {
  }
}