#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define ff first
#define ss second
ll ttt;
const ll INF=1e18;
const ll MOD=1e9+7;
const ll N=5007;
const ll K=5007;
ll n,m,k;
vector<ll>g[N];
ll b[K][N],s[K][N];
ll maxval[N];
ll dist[N][N];
void floyd_warshall(){
for(int p=1;p<=n;p++){
for(int v=1;v<=n;v++){
for(int u=1;u<=n;u++){
dist[v][u]=min(dist[v][u],dist[v][p]+dist[p][u]);
}
}
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
// freopen("output.txt","w",stdout);
cin>>n>>m>>k;
for(int i=1;i<=n;i++){
for(int j=1;j<=k;j++){
cin>>b[i][j]>>s[i][j];
}
}
for(int v=1;v<=n;v++){
for(int u=1;u<=n;u++){
dist[v][u]=INF;
if(v==u)dist[v][u]=0;
}
}
for(int i=0;i<m;i++){
ll x,y,t;
cin>>x>>y>>t;
g[x].push_back(y);
dist[x][y]=min(dist[x][y],t);
}
floyd_warshall();
// for(int v=1;v<=n;v++){
// for(int u=1;u<=n;u++){
// cout<<v<<", "<<u<<": "<<dist[v][u]<<endl;
// }
// }
ll ans=0;
for(int i=1;i<=k;i++){
if(b[1][i]!=-1){
for(int v=2;v<=n;v++){
if(s[v][i]!=-1)maxval[i]=max(maxval[i],(s[v][i]-b[1][i])/(dist[1][v]+dist[v][1]));
}
ans=max(ans,maxval[i]);
}
}
cout<<ans<<endl;
}
