#include <bits/stdc++.h>
using namespace std;
vector<vector<pair<int,int>>> items;
vector<vector<pair<int,int>>> lst;
vector<int> visited;
vector<pair<vector<int>,int>> ans;
vector<vector<int>> dist;
int n;
void fw(){
for(int i=0;i<n;i++){
for(int j=0;j<n;j++){
for(int k=0;k<n;k++){
if(dist[i][j] > dist[i][k]+dist[k][j] and dist[i][k]!=1e9 and dist[k][j]!=1e9){
dist[i][j] = dist[i][k]+dist[k][j];
}
}
}
}
}
int main(){
int m,k,v,w,t;
cin >> n >> m >> k;
// items --> vector[market][item][0-->buy / 1-->sell]
items = vector<vector<pair<int,int>>>(n,vector<pair<int,int>>(k));
dist = vector<vector<int>>(n,vector<int>(n,1e9));
for(int i=0;i<n;i++) dist[i][i]=0;
for(int i=0;i<n;i++){
for(int j=0;j<k;j++){
cin >> items[i][j].first >> items[i][j].second;
}
}
for(int i=0;i<m;i++){
cin >> v >> w >> t;
dist[v-1][w-1]=t;
}
// busco cíclos
fw();
int res = 0;
for(int i=1;i<n;i++){
for(int j=0;j<k;j++){
if(items[0][j].first==-1) continue;
if(items[i][j].second==-1) continue;
res = max(res, (items[i][j].second-items[0][j].first)/(dist[0][i]+dist[i][0]));
}
}
cout << res << endl;
}
