#include <bits/stdc++.h>




namespace zawa {

using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;
using i128 = __int128_t;

using u8 = std::uint8_t;
using u16 = std::uint16_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;

using usize = std::size_t;

} // namespace zawa


namespace zawa {

void SetFastIO() {
    std::cin.tie(nullptr)->sync_with_stdio(false);
}

void SetPrecision(u32 dig) {
    std::cout << std::fixed << std::setprecision(dig);
}

} // namespace zawa
using namespace zawa;

int main() {
    SetFastIO();

    int n, m; std::cin >> n >> m;
    int s, t, k; std::cin >> s >> t >> k;
    s--; t--;
    std::vector g(n, std::vector<int>{});
    for (int _{} ; _ < m ; _++) {
        int a, b; std::cin >> a >> b;
        a--; b--;
        g[a].emplace_back(b);
        g[b].emplace_back(a);
    }
    std::vector<int> col(n, -1);
    auto dfs{[&](auto dfs, int v, int c) -> bool {
        col[v] = c;
        for (auto x : g[v]) {
            if (col[x] != -1 and c == col[x]) return false;
            if (col[x] == -1 and !dfs(dfs, x, c ^ 1)) return false;
        }
        return true;
    }};
    const int INF{(int)1e9};
    std::vector<int> dist(n, INF);
    dist[s] = 0;
    std::queue<int> que;
    que.emplace(s);
    while (que.size()) {
        auto v{que.front()};
        que.pop();
        for (auto x : g[v]) {
            if (dist[x] > dist[v] + 1) {
                dist[x] = dist[v] + 1;
                que.emplace(x);
            }
        }
    }
    assert(dfs(dfs, s, 0));
    if (s == t) {
        if (k % 2) {
            std::cout << "No" << '\n';
        }
        else if (n == 1) {
            std::cout << "No" << '\n';
        }
        else if (g[s].size()) {
            std::cout << "Yes" << '\n';
        }
        else {
            std::cout << "Unknown" << '\n';
        }
    }
    else if (col[t] == 0) {
        assert(false);
        if (k % 2) {
            std::cout << "No" << '\n';
        }
        else if (dist[t] <= k) {
            std::cout << "Yes" << '\n';
        }
        else {
            std::cout << "Unknown" << '\n';
        }
    }
    else if (col[t] == 1) {
        assert(false);
        if (!(k % 2)) {
            std::cout << "No" << '\n';
            return 0;
        }
        else if (dist[t] <= k) {
            std::cout << "Yes" << '\n';
        }
        else {
            std::cout << "Unknown" << '\n';
        }
    }
    else {
        assert(false);
        assert(n >= 2);
        if (n == 2) {
            std::cout << (k % 2 ? "Yes" : "No") << '\n';
        }  
        else {
            std::cout << "Unknown" << '\n';
        }
    }
}