#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long
signed main() {
int n, m, k;
cin >> n >> m >> k;
vector<vector<int>> status(n, vector<int>(2 * k));
for (auto &a : status) {
for (auto &b : a)
cin >> b;
}
const int bign = 1e18;
vector<vector<int>> adjmat(n, vector<int>(n, bign));
for (int i = 0; i < m; i++) {
int a, b, t;
cin >> a >> b >> t;
a--, b--;
adjmat[a][b] = t;
}
for (int i = 0; i < n; i++)
adjmat[i][i] = 0;
for (int rounds = 0; rounds < 6; rounds++)
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
for (int k = 0; k < n; k++)
if (adjmat[i][k] != bign && adjmat[k][j] != bign)
adjmat[i][j] = min(adjmat[i][j], adjmat[i][k] + adjmat[k][j]);
vector<vector<int>> maxp(n, vector<int>(n, 0));
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
for (int in = 0; in < k; in++) {
if (status[i][in * 2] != -1 && status[j][in * 2 + 1] != -1)
maxp[i][j] =
max(maxp[i][j], status[j][in * 2 + 1] - status[i][in * 2]);
}
}
}
ll l = 0, r = 1e9, ans = 0;
while (l <= r) {
int mid = (l + r) / 2;
vector<vector<int>> mat(n, vector<int>(n));
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++)
mat[i][j] = mid * adjmat[i][j] - maxp[i][j];
}
for (int i = 0; i < n; i++)
mat[i][i] = bign;
for (int rounds = 0; rounds < 6; rounds++)
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
for (int k = 0; k < n; k++)
mat[i][j] = min(mat[i][j], max(-bign, mat[i][k] + mat[k][j]));
for (int i = 0; i < n; i++)
if (mat[i][i] <= 0) {
l = mid + 1;
ans = mid;
goto A;
}
r = mid - 1;
A:;
}
cout << ans << "\n";
}
