#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
using namespace std;
#define int long long int
const int N = 1e6 + 10;
const int md = 1e9 + 7;
const int INF = 1e12;
vector<int> dijkstra(vector<vector<pair<int, int>>> &g, int start) {
vector<int> dist(g.size(), INF);
vector<bool> visited(g.size());
set<pair<int, int>> q;
dist[start] = 0;
q.insert({0, start});
while (!q.empty()) {
int v = (*q.begin()).second;
q.erase(q.begin());
if (!visited[v])
for (auto i : g[v]) {
dist[i.first] = min(dist[i.first], dist[v] + i.second);
if (!visited[i.first])
q.insert({dist[i.first], i.first});
}
visited[v] = 1;
}
return dist;
}
int32_t main(int32_t argc, char *argv[]) {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int T = 1;
// cin >> T;
while (T--) {
int n, m, k;
cin >> n >> m >> k;
vector<vector<int>> b(n + 1, vector<int> (k + 1)), s(n + 1, vector<int> (k + 1));
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= k; j++)
cin >> b[i][j] >> s[i][j];
}
vector<vector<pair<int, int>>> g(n + 1, vector<pair<int, int>> ()), rg(n + 1, vector<pair<int, int>> ());
for (int i = 0; i < m; i++) {
int u, v, w;
cin >> u >> v >> w;
g[u].push_back({v, w});
rg[v].push_back({u, w});
}
vector<vector<int>> dist(2, vector<int> ());
dist[0] = dijkstra(g, 1);
dist[1] = dijkstra(rg, 1);
int ans = 0;
for (int i = 2; i <= n; i++) {
for (int j = 1; j <= k; j++) {
if (s[i][j] != -1 && b[1][j] != -1 && (s[i][j] - b[1][j]) > 0) {
ans = max(ans, (s[i][j] - b[1][j]) / (dist[0][i] + dist[1][i]));
}
}
}
cout << ans << '\n';
}
return 0;
}
