#include <iostream>
#include <vector>
using namespace std;
// APIO 2017 Merchant
vector<vector<long long>> d, max_delta, d1;
struct node {
long long v, w;
};
vector<vector<node>> gp;
vector<vector<long long>> b, s;
int main()
{
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n, m, k; cin >> n >> m >> k;
gp = vector<vector<node>>(n);
d = vector<vector<long long>>(n, vector<long long> (n, 1e18));
b = s = vector<vector<long long>>(n, vector<long long>(k));
for (int i = 0; i < n; ++i) {
for (int j = 0; j < k; ++j) {
cin >> b[i][j] >> s[i][j];
}
}
vector<pair<int, int>> edges;
for (int i = 0; i < m; ++i) {
int u, v, w; cin >> u >> v >> w;
--u, --v;
gp[u].push_back({ v, w });
d[u][v] = w;
edges.push_back({ u, v });
}
//return 0;
for (int k = 0; k < n; ++k) {
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
}
}
}
max_delta = vector<vector<long long>>(n, vector<long long>(n));
for (int p = 0; p < k; ++p) {
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
if (s[j][p] == -1 || b[i][p] == -1) continue;
max_delta[i][j] = max(max_delta[i][j], s[j][p] - b[i][p]);
}
}
}
// p/t >= m
//p >= t*m;
// p - t*m >= 0
d1 = vector<vector<long long>> (n, vector<long long>(n, -1e18));
long long l = 0, r = 1e11;
while (l + 1 < r) {
long long m = (l + r) / 2;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
int u = i;
int v = j;
long long p = 1e18 / m;
d1[u][v] = max_delta[u][v] - m * min(p, d[u][v]);
}
}
for (int k = 0; k < n; ++k) {
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
d1[i][j] = max(d1[i][j], d1[i][k] + d1[k][j]);
}
}
}
bool f = 0;
for (int i = 0; i < n; ++i) if (d1[i][i] >= 0) f = 1;
d1 = vector<vector<long long>>(n, vector<long long>(n, -1e18));
if (f) l = m;
else r = m;
}
cout << l << '\n';
}
