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 = -1; } else if (N == 2) { ans = ((S == T) == (K % 2 == 0)) ? (M ? +1 : 0) : -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; if (K % 2 == 0 && S == T && graph[S].empty) { ans = 0; } } 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) { } }