#include <bits/stdc++.h>
using namespace std;
const int inf = int(1e9) + 9;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m, k;
cin >> n >> m >> k;
vector<vector<int>> B(n + 1, vector<int>(k + 1)), S = B;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= k; j++) {
cin >> B[i][j] >> S[i][j];
}
}
vector<vector<int>> D(n + 1, vector<int>(n + 1, inf));
while (m--) {
int u, v, w;
cin >> u >> v >> w;
D[u][v] = w;
}
for (int i = 1; i <= n; i++) {
D[i][i] = 0;
}
for (int x = 1; x <= n; x++) {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
D[i][j] = min(D[i][j], D[i][x] + D[x][j]);
}
}
}
int ans = 0;
for (int i = 1; i <= k; i++) {
for (int j = 2; j <= n; j++) {
if (D[1][j] == inf || D[j][1] == inf || B[1][i] == -1 || S[j][i] == -1) continue;
int t = D[1][j] + D[j][1];
int prof = S[j][i] - B[1][i];
ans = max(ans, prof / t);
}
}
cout << ans << '\n';
return 0;
}
