#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "C:\GCC\debug.h"
#else
#define debug(...) void(42)
#endif
const long long inf = 1000000000000000;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, m, k;
cin >> n >> m >> k;
vector<vector<int>> b(n, vector<int> (k));
vector<vector<int>> s(n, vector<int> (k));
for (int i = 0; i < n; i++) {
for (int j = 0; j < k; j++) {
cin >> b[i][j] >> s[i][j];
}
}
vector<vector<array<int, 2>>> adj(n);
for (int i = 0; i < m; i++) {
int u, v, w;
cin >> u >> v >> w;
--u, --v;
adj[u].push_back({v, w});
}
auto Dijkstra = [&](int start) {
vector<long long> d(n, inf);
d[start] = 0;
priority_queue<array<long long, 2>, vector<array<long long, 2>>, greater<array<long long, 2>>> pQue;
pQue.push({d[start], start});
while (!pQue.empty()) {
auto x = pQue.top();
pQue.pop();
int u = x[1];
long long dist = x[0];
if (d[u] != dist) {
continue;
}
for (auto v : adj[u]) {
if (d[v[0]] > dist + v[1]) {
d[v[0]] = dist + v[1];
pQue.push({d[v[0]], v[0]});
}
}
}
return d;
};
long long ret = 0;
for (int i = 0; i < k; i++) {
if (s[0][i] > b[0][i]) {
ret += s[0][i] - b[0][i];
}
}
long long min_distance = inf;
for (auto v : adj[0]) {
vector<long long> d = Dijkstra(v[0]);
min_distance = min(min_distance, d[0] + v[1]);
}
cout << ret / min_distance << '\n';
return 0;
}
