#include "bits/stdc++.h"
using namespace std;
#ifdef Nero
#include "Deb.h"
#else
#define debug(...)
#endif
const int N = 102;
const int K = 1003;
int n;
int adj[N][N];
int best[N][N];
long long p[N][N];
long long adj2[N][N];
int buy[N][K], sell[N][K];
void floyd() {
for (int l = 1; l <= n; ++l) {
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) {
adj2[i][j] = min(adj2[i][j], adj2[i][l] + adj2[l][j]);
}
}
}
}
void floyd2() {
for (int l = 1; l <= n; ++l) {
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) {
p[i][j] = max(p[i][j], p[i][l] + p[l][j]);
}
}
}
}
bool check(int mid) {
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) {
adj2[i][j] = (long long) adj[i][j] * mid;
}
}
floyd();
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) {
p[i][j] = -adj2[i][j] + best[i][j];
}
}
floyd2();
for (int i = 1; i <= n; ++i) {
if (p[i][i] >= 0) {
return true;
}
}
return false;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int m, k;
cin >> n >> m >> k;
for (int i = 1; i <= n; ++i) {
for (int j = 2; j <= 2 * k; j += 2) {
cin >> buy[i][j / 2] >> sell[i][j / 2];
}
}
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) {
for (int l = 1; l <= k; ++l) {
if (sell[j][l] != -1 && buy[i][l] != -1) {
best[i][j] = max(best[i][j], sell[j][l] - buy[i][l]);
}
}
}
}
memset(adj, 0x3f3f3f3f, sizeof adj);
for (int i = 0; i < m; ++i) {
int u, v, w;
cin >> u >> v >> w;
adj[u][v] = min(adj[u][v], w);
}
int lo = 0, hi = 1e9 + 9;
while (lo < hi) {
int mid = (lo + hi + 1) / 2;
if (check(mid)) {
lo = mid;
} else {
hi = mid - 1;
}
}
cout << lo << '\n';
return 0;
}
