#include<bits/stdc++.h>
using namespace std;
const int nax = 101;
const long long INF = 1e18;
int n, m, k;
long long b[nax][nax*10], s[nax][nax*10];
long long graph[nax][nax], graph2[nax][nax];
long long profit[nax][nax];
void floyd_warshall(long long g[nax][nax]) {
for(int y=1; y<=n; ++y) {
for(int x=1; x<=n; ++x) {
for(int z=1; z<=n; ++z) {
g[x][z] = min(g[x][z], g[x][y]+g[y][z]);
}
}
}
}
void PlayGround() {
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) {
graph[i][j] = INF;
}
}
for(int i=0; i<m; ++i) {
int u, v, w;
cin>>u>>v>>w;
graph[u][v] = w;
}
floyd_warshall(graph);
for(int x=1; x<=k; ++x) {
for(int i=1; i<=n; ++i) {
if(b[i][x]==-1) continue;
for(int j=1; j<=n; ++j) {
if(s[j][x]==-1) continue;
profit[i][j] = max(profit[i][j], s[j][x] - b[i][x]);
}
}
}
long long lo = 0, hi = INF;
while(lo<hi) {
long long mid = (1+lo+hi) / 2;
for(int i=1; i<=n; ++i) {
for(int j=1; j<=n; ++j) {
graph2[i][j] = mid * min(graph[i][j], INF/mid) - profit[i][j];
}
}
floyd_warshall(graph2);
bool ok = false;
for(int i=1; i<=n; ++i) if(graph2[i][i]<=0) {
ok = true;
}
if(ok) lo = mid;
else hi = mid-1;
}
cout<<lo<<'\n';
//cerr<<"Time elapsed: "<<1.0*clock()/CLOCKS_PER_SEC<<" s.\n";
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
PlayGround();
return 0;
}
