#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const ll INF = 1e18;
const ld INF_DOUBLE = 1e18;
struct Market {
vector<ll> B;
vector<ll> S;
};
ll N, M, K;
ll v, w, t;
vector<Market> BSMarkets;
vector<vector<ll> > adjMat;
vector<vector<pair<ll, ll> > > adjList; // {neighbor, distance}
void takeInput() {
cin.tie(0);
ios_base::sync_with_stdio(false);
cin >> N >> M >> K;
BSMarkets.resize(N);
for (ll i = 0; i < N; i++) {
BSMarkets[i].B.resize(K);
BSMarkets[i].S.resize(K);
for (ll j = 0; j < K; j++) {
cin >> BSMarkets[i].B[j] >> BSMarkets[i].S[j];
}
}
adjList.resize(N);
adjMat.resize(N, vector<ll>(N, INF));
cin >> M;
for (ll i = 0; i < M; i++) {
cin >> v >> w >> t;
v--; w--;
adjList[v].push_back({w, t});
adjMat[v][w] = t;
}
}
ll subtask1() {
for (ll k = 0; k < N; k++) {
for (ll i = 0; i < N; i++) {
for (ll j = 0; j < N; j++) {
adjMat[i][j] = min(adjMat[i][j], adjMat[i][k] + adjMat[k][j]);
}
}
}
vector<pair<ll, ll> > buyable; // {index, price}
for (ll i = 0; i < K; i++) {
if (BSMarkets[0].B[i] != -1) {
buyable.push_back({i, BSMarkets[0].B[i]});
}
}
ll bestPossible = 0;
for (ll i = 0; i < N; i++) {
if (i == 0) continue;
for (auto item: buyable) {
if (BSMarkets[i].S[item.first] == -1) continue;
if (adjMat[0][i] == INF || adjMat[i][0] == INF) continue;
ll currentDist = adjMat[0][i] + adjMat[i][0];
bestPossible = max(bestPossible, (BSMarkets[i].S[item.first] - item.second) / currentDist);
}
}
return bestPossible;
}
int main() {
takeInput();
ll res = subtask1();
cout << res << endl;
}
