#include <bits/stdc++.h>
#include <bits/extc++.h>
#define ll long long
#define mp make_pair
#define pb push_back
#define ff first
#define ss second
#define FOR(i, x, y) for (int i = x; i < y; i++)
using namespace std;
//limit definitions
#define N 202020
int n, m, x;
ll b[101][1001], s[101][1001];
ll graph[101][101], profit[101][101], graph2[101][101];
void floyd_warshall(ll adj[101][101]) {
FOR(i, 1, n + 1)
FOR(j, 1, n + 1)
FOR(k, 1, n + 1)
adj[j][k] = min(adj[j][k], adj[j][i] + adj[i][k]);
}
int main() {
iostream::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m >> x;
FOR(i, 1, n + 1) {
FOR(j, 1, n + 1) graph[i][j] = INT_MAX;
FOR(j, 1, x + 1) cin >> b[i][j] >> s[i][j];
}
FOR(i, 0, m) {
int u, v, w;
cin >> u >> v >> w;
graph[u][v] = w;
}
floyd_warshall(graph);
FOR(i, 1, n + 1) FOR(j, 1, n + 1) FOR(k, 1, x + 1)
if (s[j][k] != -1 && b[i][k] != -1)
profit[i][j] = max(profit[i][j], s[j][k] - b[i][k]);
ll l = 1, r = 1e9;
while (l <= r) {
ll mid = (l + r) / 2;
FOR(i, 1, n + 1) FOR(j, 1, n + 1)
graph2[i][j] = mid * min(graph[i][j], INT_MAX / mid) - profit[i][j];
floyd_warshall(graph2);
bool has_nonnegative_cycle = false;
FOR(i, 1, n + 1) if (graph2[i][i] <= 0) has_nonnegative_cycle = true;
if (has_nonnegative_cycle) l = mid + 1;
else r = mid - 1;
}
cout << r;
return 0;
}
