#ifndef HIDDEN_IN_VS // 折りたたみ用 #include using namespace std; // 型名の短縮 using ll = long long; using ull = unsigned long long; // -2^63 ~ 2^63 = 9 * 10^18(int は -2^31 ~ 2^31 = 2 * 10^9) using pii = pair; using pll = pair; using pil = pair; using pli = pair; using vi = vector; using vvi = vector; using vvvi = vector; using vvvvi = vector; using vl = vector; using vvl = vector; using vvvl = vector; using vvvvl = vector; using vb = vector; using vvb = vector; using vvvb = vector; using vc = vector; using vvc = vector; using vvvc = vector; using vd = vector; using vvd = vector; using vvvd = vector; template using priority_queue_rev = priority_queue, greater>; template bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; } template bool chmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; } #define all(a) a.begin(),a.end() #define rep(i, n) for(int i = 0, i##_end = int(n); i < i##_end; ++i) // 0 から n-1 まで昇順 #define repi(i, s, t) for(int i = int(s), i##_end = int(t); i <= i##_end; ++i) // s から t まで昇順 #define repir(i, s, t) for(int i = int(s), i##_end = int(t); i >= i##_end; --i) // s から t まで降順 #define repe(v, a) for(const auto& v : (a)) // a の全要素(変更不可能) #define repea(v, a) for(auto& v : (a)) // a の全要素(変更可能) #define repb(set, d) for(int set = 0; set < (1 << int(d)); ++set) // d ビット全探索(昇順) #define repp(a) sort(all(a)); for(bool a##_perm = true; a##_perm; a##_perm = next_permutation(all(a))) // a の順列全て(昇順) #define smod(n, m) ((((n) % (m)) + (m)) % (m)) // 非負mod #define uniq(a) {sort(all(a)); (a).erase(unique(all(a)), (a).end());} // 重複除去 // template inline T smod(T n, T m) { n %= m; if (n < 0) n += m; return n; } // 非負mod long long TEN(int x) { return x == 0 ? 1 : TEN(x - 1) * 10; } #include using namespace atcoder; #endif using mint = modint998244353; #if !defined(__clang__) && defined(__GNUC__) #include "local.hpp" #else #define dump(...) #define dumpel(v) #endif struct fast_io { fast_io() { cin.tie(nullptr); ios::sync_with_stdio(false); } } fastIOtmp; int main() { ll n,m,p,y; cin >> n >> m >> p >> y; vector>> E(n); rep(i,m){ ll a,b,c; cin >> a >> b >> c; a--;b--; E[a].push_back({b,c}); E[b].push_back({a,c}); } map mp; rep(i,p){ ll d,e; cin >> d >> e; d--; mp[d]=e; } priority_queue_rev> pq; pq.push({0,0}); ll inf = 4004004004004004004; vl view(n,inf); ll ans = 0; while(!pq.empty()){ auto [t,u] = pq.top();pq.pop(); if (view[u]!=inf) continue; view[u]=t; if (mp.count(u)>0){ chmax(ans,(y-t)/mp[u]); } for(auto[v,tx]:E[u]){ if (view[v]==inf){ pq.push({t+tx,v}); } } } cout << ans << endl; }