//
// Created by mihai145 on 24.02.2021.
//
#include <iostream>
#include <vector>
#include <queue>
using namespace std;
const int NMAX = 100;
const int KMAX = 1000;
const long long INF = 1e9;
int N, M, K;
long long buy[NMAX + 2][KMAX + 2], sell[NMAX + 2][KMAX + 2];
long long bestProfit[NMAX + 2][NMAX + 2], minTime[NMAX + 2][NMAX + 2];
void CalcBestProfit() {
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= N; j++) {
for (int k = 1; k <= K; k++) {
if (sell[j][k] != -1 && buy[i][k] != -1) {
bestProfit[i][j] = max(bestProfit[i][j], sell[j][k] - buy[i][k]);
}
}
}
}
}
void CalcMinTime() {
for (int k = 1; k <= N; k++) {
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= N; j++) {
minTime[i][j] = min(minTime[i][j], minTime[i][k] + minTime[k][j]);
}
}
}
}
long long mt[NMAX + 2][NMAX + 2];
bool Can(long long R) {
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= N; j++) {
mt[i][j] = bestProfit[i][j] - R * minTime[i][j];
}
}
for (int k = 1; k <= N; k++) {
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= N; j++) {
mt[i][j] = max(mt[i][j], mt[i][k] + mt[k][j]);
}
}
}
for (int i = 1; i <= N; i++) {
if (mt[i][i] >= 0) {
return true;
}
}
return false;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> N >> M >> K;
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= K; j++) {
cin >> buy[i][j] >> sell[i][j];
}
}
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= N; j++) {
minTime[i][j] = INF;
}
}
for (int i = 1; i <= M; i++) {
int u, v, t;
cin >> u >> v >> t;
minTime[u][v] = t;
}
CalcBestProfit();
CalcMinTime();
long long st = 0, dr = INF, sol = 0;
while (st <= dr) {
long long mid = (st + dr) >> 1;
if (Can(mid)) {
sol = mid;
st = mid + 1;
} else {
dr = mid - 1;
}
}
cout << sol << '\n';
return 0;
}
