#include <bits/stdc++.h>
#define ll long long
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define pb push_back
#define FIO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
using namespace std;
typedef pair <ll, ll> pii;
const int N = 107, K = 1007;
const ll inf = 1e18;
int n, m, k;
ll b[N][K], s[N][K], d[N][N], pr[N][N], dis[N][N];
void Min(ll& x, ll y) {x = min(x, y);}
void Max(ll& x, ll y) {x = max(x, y);}
int main () {
FIO;
cin >> n >> m >> k;
for (int i = 1; i <= n; i++) for (int j = 1; j <= n; j++) d[i][j] = inf;
for (int i = 1; i <= n; i++) {
d[i][i] = 0;
for (int j = 1; j <= k; j++) {
cin >> b[i][j] >> s[i][j];
}
}
for (int i = 1; i <= m; i++) {
ll x, y, w; cin >> x >> y >> w;
d[x][y] = w;
}
for (int ii = 1; ii <= n; ii++) {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
Min(d[i][j], d[i][ii] + d[ii][j]);
}
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
if (d[i][j] == inf) continue;
pr[i][j] = 0;
for (int ii = 1; ii <= k; ii++) {
if (b[i][ii] != -1 && s[j][ii] != -1) Max(pr[i][j], s[j][ii] - b[i][ii]);
}
}
}
ll lo = 0, hi = 1e7;
while (lo < hi) {
ll mid = (lo + hi + 1) / 2;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
if (d[i][j] == inf || i == j) dis[i][j] = inf;
else dis[i][j] = -pr[i][j] + d[i][j] * mid;
}
}
for (int ii = 1; ii <= n; ii++) {
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
Min(dis[i][j], dis[i][ii] + dis[ii][j]);
}
}
}
int ok = 0;
for (int i = 1; i <= n; i++) {
ok |= (dis[i][i] <= 0);
}
if (ok) lo = mid;
else hi = mid-1;
}
cout << lo << "\n";
return 0;
}
