#include <iostream>
#include <cassert>
#include <vector>
using namespace std;
using ll = long long;
const ll INF = 1.77013e15;
const int MAXN = 100;
const int MAXK = 1000;
ll buy[MAXN][MAXK];
ll sell[MAXN][MAXK];
vector<pair<int, ll>> edg[MAXN];
vector<pair<int, ll>> redg[MAXN];
ll d[MAXN][MAXN];
ll prof[MAXN][MAXN];
ll smoke[MAXN][MAXN];
ll immortal[MAXN][MAXN];
signed main() {
int n, m, k;
cin >> n >> m >> k;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < k; ++j) {
cin >> buy[i][j] >> sell[i][j];
if (buy[i][j] == -1)
buy[i][j] = INF;
if (sell[i][j] == -1)
sell[i][j] = 0;
}
}
for (int i = 0; i < m; ++i) {
int u, v, w;
cin >> u >> v >> w;
--u, --v;
edg[u].push_back({v, w});
edg[v].push_back({u, w});
}
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
d[i][j] = INF;
}
d[i][i] = 0;
for (auto [v, dv] : edg[i]) {
d[i][v] = dv;
}
}
for (int i = 0; i < n; ++i) {
for (int v = 0; v < n; ++v) {
for (int u = 0; u < n; ++u) {
d[v][u] = min(d[v][u], d[v][i] + d[i][u]);
}
}
}
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
for (int w = 0; w < n; ++w) {
assert(d[i][j] + d[j][w] >= d[i][w]);
}
}
}
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
for (int t = 0; t < k; ++t) {
prof[i][j] = max(prof[i][j], sell[j][t] - buy[i][t]);
}
}
assert(prof[i][i] == 0);
}
ll lb = 0, ub = INF;
while (ub - lb > 1) {
ll mb = (lb + ub) / 2;
// (sum prof) / (sum time) >= mb
// sum prof >= mb * (sum time)
// sum {prof - mb * time} >= 0
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
if (d[i][j] == INF || prof[i][j] == 0)
smoke[i][j] = -INF;
else
smoke[i][j] = prof[i][j] - mb * d[i][j];
immortal[i][j] = smoke[i][j];
}
}
for (int i = 0; i < n; ++i) {
for (int v = 0; v < n; ++v) {
for (int u = 0; u < n; ++u) {
immortal[v][u] = max(immortal[v][u], immortal[v][i] + immortal[i][u]);
}
}
}
for (int i = 0; i < n; ++i) {
if (immortal[i][i] > 0) {
lb = mb;
}
}
if (lb != mb)
ub = mb;
}
cout << lb << endl;
}
