#include <bits/stdc++.h>
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
#define endl '\n'
const int MXN = 100;
const ll INF = 1e15;
ll dist[MXN+1][MXN+1], gain[MXN+1][MXN+1], aux[MXN+1][MXN+1];
int main() {
#ifdef shiven
freopen("test.in", "r", stdin);
#endif
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m, k; cin >> n >> m >> k;
vector<vector<vector<ll>>> cost(n, vector<vector<ll>>(k, vector<ll>(2)));
for_(i, 0, n) for_(j, 0, k) cin >> cost[i][j][0] >> cost[i][j][1];
for_(i, 0, m) {
int a, b, w; cin >> a >> b >> w;
a -= 1; b -= 1;
dist[a][b] = w; dist[b][a] = w;
}
for_(i, 0, n) for_(j, 0, n) if (!dist[i][j]) dist[i][j] = INF;
for_(p, 0, n) for_(i, 0, n) for_(j, 0, n) dist[i][j] = min(dist[i][j], dist[i][k]+dist[k][j]);
for_(i, 0, n) for_(j, 0, n) if (i != j) {
for_(p, 0, k) if (cost[i][p][0] != -1 and cost[j][p][1] != -1) gain[i][j] = max(gain[i][j], cost[j][p][1]-cost[i][p][0]);
}
ll lo = 0, hi = 1e11+1, ans = 0;
while (lo < hi) {
ll mid = (lo+hi) / 2;
for_(i, 0, n) for_(j, 0, n) {
if (dist[i][j] != INF) aux[i][j] = mid * dist[i][j] - gain[i][j];
else aux[i][j] = INF;
}
bool valid = false;
for_(p, 0, n) for_(i, 0, n) for_(j, 0, n) aux[i][j] = min(aux[i][j], aux[i][k]+aux[k][j]);
for_(i, 0, n) if (aux[i][i] <= 0) {
valid = true;
//cout << mid << " " << aux[i][i] << endl;
break;
}
if (valid) {
lo = mid+1; ans = mid;
} else hi = mid;
}
cout << ans << endl;
return 0;
}
