#include<bits/stdc++.h>
using namespace std;
#define pli pair<ll,int>
#define ll long long
int N, M, K;
ll B[105][1005], S[105][1005], mindis[105][105], profit[105][105];
double ans[105][105];
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
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 i=1;i<=N;i++) {
for(int j=1;j<=N;j++) mindis[i][j] = 1e18;
mindis[i][i] = 0;
}
while(M--) {
int u, v; ll w;
cin>>u>>v>>w;
mindis[u][v] = min(mindis[u][v], w);
}
for(int k=1;k<=N;k++) for(int i=1;i<=N;i++) for(int j=1;j<=N;j++) {
mindis[i][j] = min(mindis[i][j], mindis[i][k]+mindis[k][j]);
}
for(int i=1;i<=N;i++) for(int j=1;j<=N;j++) {
for(int k=1;k<=K;k++) {
if(B[i][k]==-1 || S[j][k]==-1) continue;
profit[i][j] = max(profit[i][j], S[j][k]-B[i][k]);
}
ans[i][j] = max(ans[i][j], (double)profit[i][j]/(double)mindis[i][j]);
}
for(int k=1;k<=N;k++) for(int i=1;i<=N;i++) for(int j=1;j<=N;j++) {
ans[i][j] = max(ans[i][j], (double)(profit[i][k]+profit[k][j])/(double)(mindis[i][k]+mindis[k][j]));
}
double mx = 0;
for(int i=1;i<=N;i++) mx = max(mx, ans[i][i]);
ll answer = mx+0.5;
cout<<answer;
}
