#include<bits/stdc++.h>
using namespace std;
const int INF = 1e9;
const int nax = 101;
vector<pair<int,int>>market[nax];
int g[nax][nax];
int dist[nax][nax];
void PlayGround() {
int n, m, k;
cin>>n>>m>>k;
for(int i=1; i<=n; ++i) {
for(int j=1; j<=k; ++j) {
int b, s;
cin>>b>>s;
market[i].emplace_back(b, s);
}
}
for(int i=1; i<=n; ++i) {
for(int j=1; j<=n; ++j) {
if(i!=j) dist[i][j] = INF;
}
}
for(int i=0; i<m; ++i) {
int u, v, w;
cin>>u>>v>>w;
g[u][v] = w;
dist[u][v] = w;
}
for(int b=1; b<=n; ++b) {
for(int a=1; a<=n; ++a) {
for(int c=1; c<=n; ++c) {
dist[a][c] = min(dist[a][c], dist[a][b]+dist[b][c]);
}
}
}
double ans = 0;
for(int item=0; item<k; ++item) {
for(int sell=2; sell<=n; ++sell) {
double profit = market[sell][item].second - market[1][item].first;
double d = dist[1][sell] + dist[sell][1];
ans = max(ans, profit / d);
}
}
cout<<floor(ans)<<'\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
PlayGround();
return 0;
}
