#include <bits/stdc++.h>
using namespace std;
namespace
{
} // namespace
void solve()
{
int n, m, k;
cin >> n >> m >> k;
vector a(n, vector<array<long, 2>>(k));
for (int u = 0; u < n; u++)
{
for (auto &[x, y] : a[u])
cin >> x >> y;
}
vector<tuple<int, int, long>> edges(m);
for (auto &[u, v, w] : edges)
cin >> u >> v >> w, --u, --v;
vector util(n, vector<long>(n));
for (int u = 0; u < n; u++)
{
for (int v = 0; v < n; v++)
{
for (int i = 0; i < k; i++)
{
if (min(a[u][i][0], a[v][i][1]) != -1)
util[u][v] = max(util[u][v], a[v][i][1] - a[u][i][0]);
}
}
}
vector dist(n, vector<long>(n, 1l << 30));
for (auto [u, v, w] : edges)
dist[u][v] = w;
for (int s = 0; s < n; s++)
{
for (int u = 0; u < n; u++)
{
for (int v = 0; v < n; v++)
dist[u][v] = min(dist[u][v], dist[u][s] + dist[s][v]);
}
}
auto check = [&](long mid) -> bool
{
vector dp(n, vector<long>(n));
for (int u = 0; u < n; u++)
{
for (int v = 0; v < n; v++)
dp[u][v] = util[u][v] - mid * dist[u][v];
}
for (int s = 0; s < n; s++)
{
for (int u = 0; u < n; u++)
{
for (int v = 0; v < n; v++)
dp[u][v] = max(dp[u][v], dp[u][s] + dp[s][v]);
}
}
for (int u = 0; u < n; u++)
{
if (dp[u][u] >= 0)
return 1;
}
return 0;
};
long lo = 0, hi = 1l << 30;
while (lo < hi)
{
long mid = (lo + hi + 1) / 2;
if (check(mid))
lo = mid;
else
hi = mid - 1;
}
cout << lo << '\n';
}
int main()
{
ios_base::sync_with_stdio(false), cin.tie(NULL);
solve();
return 0;
}
