#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
#define ii pair<int,int>
const int N = 105;
const int K = 1010;
int buy[N][K];
int sell[N][K];
int n, m, k;
vector<ii> adj[N];
int dis[N][N];
signed main(){
cin >> n >> m >> k;
for(int i=0; i<n; ++i){
for(int j=0; j<k; ++j){
cin >> buy[i][j] >> sell[i][j];
}
}
for(int i=0; i<n; ++i){
for(int j=0; j<n; ++j){
dis[i][j] = 4e18;
}
dis[i][i] = 0;
}
for(int i=0; i<m; ++i){
int u, v, w;
cin >> u >> v >> w;
u--, v--;
adj[u].push_back({v, w});
dis[u][v] = min(dis[u][v], w);
}
// floyd
for(int p=0; p<n; ++p){
for(int u=0; u<n; ++u){
for(int v=0; v<n; ++v){
dis[u][v] = min(dis[u][v], dis[u][p] + dis[p][v]);
}
}
}
int ans = 0;
for(int i=0; i<k; ++i){
// suppose I'm buying the ith item
if(buy[0][i] == -1) continue;
for(int p=0; p<n; ++p){
if(sell[p][i] == -1) continue;
// I sell it in market p
int profit = sell[p][i] - buy[0][i];
profit /= dis[0][p] + dis[p][0];
ans = max(ans, profit);
}
}
cout << ans << endl;
}
