//#define _GLIBCXX_DEBUG
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
//#include <ext/pb_ds/assoc_container.hpp>
//
//using namespace __gnu_pbds;
//
//template<typename T>
//using ordered_set = tree<T, null_type, less < T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T>
using normal_queue = priority_queue<T, vector<T>, greater<>>;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
#define ll long long
#define trace(x) cout << #x << ": " << (x) << endl;
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define uniq(x) x.resize(unique(all(x)) - begin(x))
#define ld long double
#define sz(s) ((int) size(s))
#define pii pair<int, int>
#define mp(x, y) make_pair(x, y)
#define int128 __int128
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
template<typename T>
bool ckmn(T &x, T y) {
if (x > y) {
x = y;
return true;
}
return false;
}
template<typename T>
bool ckmx(T &x, T y) {
if (x < y) {
x = y;
return true;
}
return false;
}
int bit(int x, int b) {
return (x >> b) & 1;
}
int rand(int l, int r) { return (int) ((ll) rnd() % (r - l + 1)) + l; }
const ll infL = 3e18;
const int infI = 1000000000 + 7;
const int infM = 2139062143;
const ll infML = 9187201950435737471LL;
const int maxN = 101, maxK = 1001;
const ll mod = 998244353;
const ld eps = 1e-9;
int N, M, K, b[maxN][maxK], s[maxN][maxK], dist[maxN][maxN];
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> N >> M >> K;
for (int i = 0; i < N; ++i) {
for (int j = 0; j < K; ++j) {
cin >> b[i][j] >> s[i][j];
}
fill(dist[i], dist[i] + N, infI);
dist[i][i] = 0;
}
for (int i = 0; i < M; ++i) {
int a, bb, w;
cin >> a >> bb >> w;
--a, --bb;
dist[a][bb] = w;
}
for (int k = 0; k < N; ++k)
for (int i = 0; i < N; ++i)
for (int j = 0; j < N; ++j)
if (dist[i][k] != infI && dist[k][j] != infI)
ckmn(dist[i][j], dist[i][k] + dist[k][j]);
int ans = 0;
for (int i = 1; i < N; ++i) {
int len = dist[0][i] + dist[i][0];
for (int j = 0; j < K; ++j) {
if (b[0][j] && s[i][j])
ckmx(ans, (s[i][j] - b[0][j]) / len);
}
}
cout << ans;
return 0;
}
