#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef double db;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define pbds tree<pair<ll, ll>, null_type, less<pair<ll,ll>>,rb_tree_tag, tree_order_statistics_node_update>
using namespace __gnu_pbds;
ll gcd(ll a , ll b) {return b ? gcd(b , a % b) : a ;} // greatest common divisor (PGCD)
ll lcm(ll a , ll b) {return (a * b) / gcd(a , b);} // least common multiple (PPCM)
int dx[8] = {1, 0, 0, -1, 1, 1, -1, -1};
int dy[8] = {0, 1, -1, 0, 1, -1, -1, 1};
#define endl "\n"
#define ss second
#define ff first
#define all(x) (x).begin() , (x).end()
#define pb push_back
#define vi vector<int>
#define vii vector<pair<int,int>>
#define vl vector<ll>
#define vll vector<pair<ll,ll>>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define vdd vector<pdd>
#define speed ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
////////////////////Only Clear Code//////////////////////////
void usaco_problem(){
freopen("milkvisits.in", "r", stdin);
freopen("milkvisits.out", "w", stdout);
}
void init(){
#ifndef ONLINE_JUDGE
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif // ONLINE_JUDGE
}
const int mx = 105;
const int LOG = 25;
const ll inf = 1e18;
const ll mod = 1e8;
int n, m, k;
vl B[mx], S[mx];
vii graph[mx];
ll adj[mx][mx];
ll distances[mx][mx];
void run_case(){
cin >> n >> m >> k;
for(int i = 1; i <= n;i++){
for(int j = 0; j < k;j++){
int x;cin >> x;
B[i].pb(x);
cin >> x;
S[i].pb(x);
}
}
memset(adj, -1, sizeof adj);
while(m--){
int a, b, w;cin >> a >> b >> w;
adj[a][b] = w;
}
for(int i = 1; i <= n;i++){
for(int j = 1; j <= n;j++){
if(i == j)distances[i][j] = 0;
else if(adj[i][j] != -1)distances[i][j] = adj[i][j];
else distances[i][j] = inf;
}
}
for(int k = 1; k <= n;k++){
for(int i = 1; i <= n;i++){
for(int j = 1; j <= n;j++){
distances[i][j] = min(distances[i][j], distances[i][k]+distances[k][j]);
}
}
}
ll ans = 0;
ll cyd = inf;
for(int i = 2; i <= n;i++){
if(distances[1][i] != inf && distances[i][1] != inf){
ll x = distances[1][i] + distances[i][1];
cyd = min(cyd, x);
ll cost = 0;
for(int j = 0;j < k;j++){
if(B[1][j] != -1 && S[i][j] != -1){
cost = max(cost, S[i][j] - B[1][j]);
}
}
ans = max(ans, cost/x);
}
}
ll cost = 0;
for(int i = 0; i < k;i++){
if(B[1][i] != -1 && S[1][i] != -1){
cost = max(cost, S[1][i] - B[1][i]);
}
}
//ans = max(ans, cost / cyd);
cout << ans << endl;
}
int main(){
//init();
speed;
int t;
//cin >> t;
t = 1;
while(t--){
run_case();
}
}
/*
NEVER GIVE UP!
DOING SMTHNG IS BETTER THAN DOING NTHNG!!!
Your Guide when stuck:
- Continue keyword only after reading the whole input
- Don't use memset with testcases
- Check for corner cases(n=1, n=0)
- Check where you declare n(Be careful of declaring it globally and in main)
*/
