import java.io.BufferedInputStream; import java.io.IOException; import java.io.PrintWriter; import java.util.*; import java.util.function.IntUnaryOperator; import java.util.function.LongUnaryOperator; import java.util.stream.Collectors; import java.util.stream.IntStream; public class Main { static In in = new In(); static Out out = new Out(false, false); static final long inf = 0x1fffffffffffffffL; static final int iinf = 0x3fffffff; static final double eps = 1e-9; static long mod = 998244353; void solve() { int n = in.nextInt(); int m = in.nextInt(); int s = in.nextInt() - 1; int t = in.nextInt() - 1; int k = in.nextInt(); List> edges = in.nextGraph(n, m, false); Deque deque = new ArrayDeque<>(); int[] dist = new int[n]; Arrays.fill(dist, iinf); dist[s] = 0; deque.addLast(s); while (!deque.isEmpty()) { Integer v = deque.removeFirst(); for (Integer u : edges.get(v)) { if (dist[u] > dist[v] + 1) { dist[u] = dist[v] + 1; deque.addLast(u); } } } if (s == t) { if (k % 2 == 1) { out.println("No"); } else if (n == 1) { out.println("No"); } else if (edges.get(s).isEmpty()) { out.println("Unknown"); } else { out.println("Yes"); } return; } if (dist[t] >= iinf) { out.println("Unknown"); } else if (dist[t] % 2 != k % 2) { out.println("No"); } else if (dist[t] <= k) { out.println("Yes"); } else { out.println("Unknown"); } } public static void main(String... args) { new Main().solve(); out.flush(); } } class In { private final BufferedInputStream reader = new BufferedInputStream(System.in); private final byte[] buffer = new byte[0x10000]; private int i = 0; private int length = 0; public int read() { if (i == length) { i = 0; try { length = reader.read(buffer); } catch (IOException ignored) { } if (length == -1) { return 0; } } if (length <= i) { throw new RuntimeException(); } return buffer[i++]; } public String next() { StringBuilder builder = new StringBuilder(); int b = read(); while (b < '!' || '~' < b) { b = read(); } while ('!' <= b && b <= '~') { builder.appendCodePoint(b); b = read(); } return builder.toString(); } public String nextLine() { StringBuilder builder = new StringBuilder(); int b = read(); while (b != 0 && b != '\r' && b != '\n') { builder.appendCodePoint(b); b = read(); } if (b == '\r') { read(); } return builder.toString(); } public int nextInt() { long val = nextLong(); if (val < Integer.MIN_VALUE || Integer.MAX_VALUE < val) { throw new NumberFormatException(); } return (int)val; } public long nextLong() { int b = read(); while (b < '!' || '~' < b) { b = read(); } boolean neg = false; if (b == '-') { neg = true; b = read(); } long n = 0; int c = 0; while ('0' <= b && b <= '9') { n = n * 10 + b - '0'; b = read(); c++; } if (c == 0 || c >= 2 && n == 0) { throw new NumberFormatException(); } return neg ? -n : n; } public double nextDouble() { return Double.parseDouble(next()); } public char[] nextCharArray() { return next().toCharArray(); } public String[] nextStringArray(int n) { String[] s = new String[n]; for (int i = 0; i < n; i++) { s[i] = next(); } return s; } public char[][] nextCharMatrix(int n, int m) { char[][] a = new char[n][m]; for (int i = 0; i < n; i++) { a[i] = next().toCharArray(); } return a; } public int[] nextIntArray(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) { a[i] = nextInt(); } return a; } public int[] nextIntArray(int n, IntUnaryOperator op) { int[] a = new int[n]; for (int i = 0; i < n; i++) { a[i] = op.applyAsInt(nextInt()); } return a; } public int[][] nextIntMatrix(int h, int w) { int[][] a = new int[h][w]; for (int i = 0; i < h; i++) { a[i] = nextIntArray(w); } return a; } public long[] nextLongArray(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) { a[i] = nextLong(); } return a; } public long[] nextLongArray(int n, LongUnaryOperator op) { long[] a = new long[n]; for (int i = 0; i < n; i++) { a[i] = op.applyAsLong(nextLong()); } return a; } public long[][] nextLongMatrix(int h, int w) { long[][] a = new long[h][w]; for (int i = 0; i < h; i++) { a[i] = nextLongArray(w); } return a; } public List> nextGraph(int n, int m, boolean directed) { List> res = new ArrayList<>(); for (int i = 0; i < n; i++) { res.add(new ArrayList<>()); } for (int i = 0; i < m; i++) { int u = nextInt() - 1; int v = nextInt() - 1; res.get(u).add(v); if (!directed) { res.get(v).add(u); } } return res; } } class Out { private final PrintWriter out = new PrintWriter(System.out); private final PrintWriter err = new PrintWriter(System.err); public boolean autoFlush; public boolean enableDebug; public Out(boolean autoFlush, boolean enableDebug) { this.autoFlush = autoFlush; this.enableDebug = enableDebug; } public void debug(Object... args) { if (!enableDebug) { return; } if (args == null || args.getClass() != Object[].class) { args = new Object[] {args}; } err.println(Arrays.stream(args).map(obj -> format(obj, true)).collect(Collectors.joining(" "))); err.flush(); } private String format(Object obj, boolean canMultiline) { if (obj == null) return "null"; Class clazz = obj.getClass(); if (clazz == Double.class) return String.format("%.10f", obj); if (clazz == int[].class) return Arrays.toString((int[])obj); if (clazz == long[].class) return Arrays.toString((long[])obj); if (clazz == char[].class) return String.valueOf((char[])obj); if (clazz == boolean[].class) return IntStream.range(0, ((boolean[])obj).length).mapToObj(i -> ((boolean[])obj)[i] ? "1" : "0").collect(Collectors.joining()); if (clazz == double[].class) return Arrays.toString(Arrays.stream((double[])obj).mapToObj(a -> format(a, false)).toArray()); if (canMultiline && clazz.isArray() && clazz.componentType().isArray()) return Arrays.stream((Object[])obj).map(a -> format(a, false)).collect(Collectors.joining("\n")); if (clazz == Object[].class) return Arrays.toString(Arrays.stream((Object[])obj).map(a -> format(a, false)).toArray()); if (clazz.isArray()) return Arrays.toString((Object[])obj); return String.valueOf(obj); } public void println(Object... args) { if (args == null || args.getClass() != Object[].class) { args = new Object[] {args}; } out.println(Arrays.stream(args) .map(obj -> obj instanceof Double ? String.format("%.10f", obj) : String.valueOf(obj)) .collect(Collectors.joining(" "))); if (autoFlush) { out.flush(); } } public void println(char a) { out.println(a); if (autoFlush) { out.flush(); } } public void println(int a) { out.println(a); if (autoFlush) { out.flush(); } } public void println(long a) { out.println(a); if (autoFlush) { out.flush(); } } public void println(double a) { out.println(String.format("%.10f", a)); if (autoFlush) { out.flush(); } } public void println(String s) { out.println(s); if (autoFlush) { out.flush(); } } public void println(char[] s) { out.println(String.valueOf(s)); if (autoFlush) { out.flush(); } } public void println(int[] a) { StringJoiner joiner = new StringJoiner(" "); for (int i : a) { joiner.add(Integer.toString(i)); } out.println(joiner); if (autoFlush) { out.flush(); } } public void println(long[] a) { StringJoiner joiner = new StringJoiner(" "); for (long i : a) { joiner.add(Long.toString(i)); } out.println(joiner); if (autoFlush) { out.flush(); } } public void flush() { err.flush(); out.flush(); } }