#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef pair<ii, int> ri3;
#define mp make_pair
#define pb push_back
#define fi first
#define sc second
#define SZ(x) (int)(x).size()
#define ALL(x) begin(x), end(x)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define FOR(i, a, b) for (int i = a; i <= b; ++i)
#define RFOR(i, a, b) for (int i = a; i >= b; --i)
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false);
cin.tie(0);
int n, m, x; cin >> n >> m >> x;
int b[n][x], s[n][x];
FOR(i, 0, n-1) {
FOR(j, 0, x-1) {
cin >> b[i][j] >> s[i][j];
}
}
int am1[n][n];
memset(am1, -1, sizeof am1);
FOR(i, 0, m-1) {
int u, v, w; cin >> u >> v >> w;
--u, --v;
am1[u][v] = w;
}
FOR(k, 0, n-1) FOR(i, 0, n-1) if (am1[i][k] != -1) FOR(j, 0, n-1) if (am1[k][j] != -1) {
if (am1[i][j] == -1 || am1[i][k]+am1[k][j]<am1[i][j])
am1[i][j] = am1[i][k]+am1[k][j];
}
int am2[n][n];
FOR(i, 0, n-1) FOR(j, 0, n-1) {
am2[i][j] = 0;
FOR(k, 0, x-1) if (s[j][k] != -1 && b[i][k] != -1) am2[i][j] = max(am2[i][j], s[j][k]-b[i][k]);
}
int lo = 0, hi = 1e9+10;
while (lo < hi) {
int mid = (lo+hi)/2;
//sum(w) / sum(dist) >= r;
//sum(w) - r*sum(dist) >= 0;
//sum(w - r*dist) >= 0;
#define NINF (-1e18)
ll am3[n][n];
FOR(i, 0, n-1) FOR(j, 0, n-1) {
if (am1[i][j] != -1) {
am3[i][j] = (ll)am2[i][j] - (ll)mid*am1[i][j];
}
else {
am3[i][j] = NINF;
}
}
FOR(k, 0, n-1) FOR(i, 0, n-1) if (am3[i][k] != NINF) FOR(j, 0, n-1) if (am3[k][j] != NINF) {
am3[i][j] = max(am3[i][j], am3[i][k]+am3[k][j]);
}
bool ok = false;
FOR(i, 0, n-1) ok |= am3[i][i] >= 0;
if (ok) lo = mid+1;
else hi = mid;
}
cout << lo-1 << '\n';
}
