#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; namespace utils{ #define ALL(x) begin(x), end(x) #define RALL(x) rbegin(x), rend(x) ///----- aliases using ll = long long int; using ull = unsigned long long; template using p_queue = priority_queue, Compare>; template using min_queue = p_queue>; template using max_queue = p_queue>; template inline bool CHMIN(T& X, const T& A){ if(X > A) {X = A; return true;} return false; } template inline bool CHMAX(T& X, const T& A){ if(X < A) {X = A; return true;} return false; } ///----- vector I/O template vector VEC(size_t n, T t){ return vector(n, t); } template auto VEC(size_t n, Ts ... ts){ return vector(n, VEC(ts...)); } template istream& operator>>(istream& is, vector& v){ for (auto &&x : v) { is >> x; } return is; } template ostream& operator<<(ostream& os, const vector& v){ auto p = v.begin(); assert(p != v.end()); os << *p++; while(p != v.end()){ os << ' ' << *p++; } return os ; } template ostream& operator<<(ostream& os, const vector>& v){ auto p = v.begin(); assert(p != v.end()); os << *p++; while(p != v.end()){ os << '\n' << *p++; } return os; } ///----- tuple I/O template istream& operator>>(istream& is, tuple& t){ return is >> get<0>(t) >> get<1>(t); } template istream& operator>>(istream& is, pair& t){ return is >> get<0>(t) >> get<1>(t); } template istream& operator>>(istream& is, tuple& t){ return is >> get<0>(t) >> get<1>(t) >> get<2>(t); } template ostream& operator<<(ostream& os, const tuple& t){ return os << get<0>(t) << ' ' << get<1>(t); } template ostream& operator<<(ostream& os, const pair& t){ return os << get<0>(t) << ' ' << get<1>(t); } template ostream& operator<<(ostream& os, const tuple& t){ return os << get<0>(t) << ' ' << get<1>(t) << ' ' << get<2>(t); } ///----- constants constexpr ll INFLL = 1'000'000'000'000'000'020ll; constexpr ll INF = 1'000'000'009; constexpr double PI = 3.14'159'265'358'979'323'846; constexpr double EPS = 1e-12; } using namespace utils; class solver{ istream& is; ostream& os; public: solver(istream& I, ostream& O) :is(I), os(O) {} int N, M; int s, t, k; vector> F; bool input() { N = M = 0; is >> N >> M; is >> s >> t >> k; s--; t--; F.resize(N); for (int i = 0; i < M; ++i) { int a, b; is >> a >> b; a--; b--; F[a].push_back(b); F[b].push_back(a); } // end i return !!is; } void run(); }; void solver::run(){ if(!input()) return; if(k < 1){ assert(1); } if(N==1){ os << "No\n"; return; } if(s == t){ if(k%2 == 1){ os << "No\n"; } else if(F[s].empty()){ os << "Unknown\n"; } else os << "Yes\n"; return; } vector d(N, -1); queue qv; qv.push(s); d[s] = 0; while(!qv.empty()){ int vi = qv.front(); qv.pop(); for (auto &&u: F[vi]) { if(d[u] == -1 or (s == u and d[u] == 0)){ qv.push(u); d[u] = d[vi] + 1; } } // end u } // not connected if(d[t] == -1){ if(N==2){ // s != t if(k % 2 != 1){ os << "No\n"; return; } } os << "Unknown\n"; return; } if((k % 2) != (d[t] % 2)){ os << "No\n"; return; } else if(d[t] <= k){ os << "Yes\n"; return; } os << "Unknown\n"; } int main(int argc, char *argv[]) { cin.tie(nullptr); ios::sync_with_stdio(false); cout << setprecision(16) << scientific; #ifdef XELMH string test_cases = "test_c.txt"; cerr << test_cases << " -->" << endl; auto fs = fstream(test_cases, fstream::in); int loop = 0; while(fs) { loop++; cout << '#' << loop << "#------\n"; solver(fs, cout).run(); } if(loop <= 1) { cout << "===" << endl; while(cin) solver(cin, cout).run(); } #else solver(cin, cout).run(); #endif return 0; }