#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define FOR(i,l,r,d) for(int i=(l);i<=(r);i+=(d))
#define szof(x) ((x).size())
#define vi vector<int>
#define pii pair<int,int>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define mkp make_pair
const int INF = 2147483647;
const int MOD = 1000000007;
const int mod = 998244353;
const double eps = 1e-12;
//#pragma GCC optimize("Ofast")
const int NMAX = 101;
const int MMAX = 9901;
const int CMAX = 1001;
/// c = n. of items
int n, m, c;
int edge[101][101];
int dis[101][101];
int buy[NMAX][CMAX], sell[NMAX][CMAX];
/// buy[][] : buy item j at market i
int res;
void FW(){
FOR(k,1,n,1){
FOR(i,1,n,1){
FOR(j,1,n,1){
dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
}
}
}
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
/// input
cin>>n>>m>>c;
FOR(i,1,n,1){
FOR(j,1,c,1){
cin>>buy[i][j]>>sell[i][j];
}
}
FOR(i,1,n,1){
FOR(j,1,n,1){
edge[i][j] = INF*INF;
}
}
FOR(i,1,m,1){
int u, v, w;
cin>>u>>v>>w;
edge[u][v] = w;
}
FOR(i,1,n,1){
FOR(j,1,n,1){
dis[i][j] = edge[i][j];
}
}
/// all-pair SP
FW();
/// init res
res = 0;
/// enumerate (destination i, item j)
FOR(i,1,n,1){
FOR(j,1,c,1){
int lc = dis[1][i] + dis[i][1]; /// len. of cycle
int pf = -buy[1][j] + sell[i][j]; /// profit
res = max(res, pf/lc);
}
}
cout<<res<<'\n';
return 0;
}
