#include <bits/stdc++.h>
#define IO_OP std::ios::sync_with_stdio(0); std::cin.tie(0);
#define F first
#define S second
#define V vector
#define PB push_back
#define MP make_pair
#define EB emplace_back
#define ALL(v) (v).begin(), (v).end()
#define double long double
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;
string _reset = "\u001b[0m", _yellow = "\u001b[33m", _bold = "\u001b[1m";
void DBG() { cerr << "]" << _reset << endl; }
template<class H, class...T> void DBG(H h, T ...t) {
cerr << to_string(h);
if(sizeof ...(t)) cerr << ", ";
DBG(t...);
}
#ifdef CHEISSMART
#define debug(...) cerr << _yellow << _bold << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define debug(...)
#endif
const int INF = 0x3f3f3f3f, N = 105, K = 1005;
const ll oo = 1e18;
const double eps = 1e-9;
int cost[N][K][2];
int a[N][N], b[N][N];
double c[N][N];
signed main()
{
IO_OP;
memset(a, 0x3f, sizeof a);
int n, m, k;
cin >> n >> m >> k;
for(int i = 0; i < n; i++)
for(int j = 0; j < k; j++) {
cin >> cost[i][j][0] >> cost[i][j][1];
}
for(int i = 0; i < n; i++)
a[i][i] = 0;
for(int i = 0; i < m; i++) {
int u, v, w;
cin >> u >> v >> w;
u--, v--;
a[u][v] = min(a[u][v], w);
}
for(int k = 0; k < n; k++)
for(int i = 0; i < n; i++)
for(int j = 0; j < n; j++)
a[i][j] = min(a[i][j], a[i][k] + a[k][j]);
for(int i = 0; i < n; i++)
for(int j = 0; j < n; j++)
for(int l = 0; l < k; l++) {
if(cost[j][l][1] != -1 && cost[i][l][0] != -1)
b[i][j] = max(b[i][j], cost[j][l][1] - cost[i][l][0]);
}
auto ok = [&] (double eff) {
// for(int i = 0; i < n; i++)
// for(int j = 0; j < n; j++) {
// if(a[i][j] < INF)
// c[i][j] = a[i][j] * eff - b[i][j];
// else
// c[i][j] = oo;
// }
// for(int k = 0; k < n; k++)
// for(int i = 0; i < n; i++)
// for(int j = 0; j < n; j++)
// c[i][j] = min(c[i][j], c[i][k] + c[k][j]);
// for(int i = 0; i < n; i++)
// if(c[i][i] < 0)
// return true;
// return false;
for(int i = 1; i < n; i++) {
int dist = a[0][i] + a[i][0];
int get = b[0][i] + b[i][0];
double ans = (double) get / dist;
if(ans > eff)
return true;
}
return false;
};
double lb = 0, rb = INF;
for(int i = 0; i < 200; i++) {
double mb = (lb + rb) / 2;
if(ok(mb)) lb = mb;
else rb = mb;
}
cout << int(lb + eps) << '\n';
}
