//#pragma GCC optomize("Ofast")
#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("O3")
//#pragma GCC target("avx2")
//#pragma GCC target("sse,sse2,sse4.1,sse4.2")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define max_heap priority_queue<pair <ll, pair <ll, ll>>>
#define min_heap priority_queue<pair <ll, ll>, vector<pair <ll, ll>>, greater<pair <ll, ll>>>
//#define min_heap priority_queue<ll, vector<ll>, greater<ll>>
#define sariE cin.tie(NULL); cout.tie(NULL); ios_base::sync_with_stdio(false);
#define filE freopen("in.txt", "r", stdin); freopen("out1.txt", "w", stdout);
#define endl '\n'
#define md(a) (a % mod + mod) % mod
#define pb push_back
//cout << vectorprecision(5) << fixed << f;
//hash prime = 769
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll const maxn = 2e5 + 123;
ll const inf = 2e9;
ll const loG = 23;
ll const mod = 1e9 + 7;
//ll const mod = 998244353;
ll const sq = 400;
ll power(ll a, ll b, ll mod){if(b==0)return 1;if(b==1)return a;ll x = power(a, b / 2, mod);return (((x * x) % mod) * (b % 2 ? a : 1)) % mod;}
ll n, m, kala, dis[110][110], yal[110][110], b[110][1001], s[110][1001], w[110][110], sid[110][110];
void Solve(){
cin >> n >> m >> kala;
for (int i = 1; i < n + 1; i++){
for (int j = 1; j < n + 1; j++)
dis[i][j] = inf;
for (int j = 1; j < kala + 1; j++){
cin >> b[i][j] >> s[i][j];
}
}
// for (int i = 1; i < n + 1; i++)
// dis[i][i] = 0;
for (int i = 1; i < m + 1; i++){
ll a, b, c; cin >> a >> b >> c;
dis[a][b] = min(dis[a][b], c);
}
for (int k = 1; k < n + 1; k++)
for (int i = 1; i < n + 1; i++)
for (int j = 1; j < n + 1; j++)
dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
for (int k = 1; k < kala + 1; k++)
for (int i = 1; i < n + 1; i++)
for (int j = 1; j < n + 1; j++)
if ((s[j][k] > -1) && (b[i][k] > -1))
w[i][j] = max(w[i][j], s[j][k] - b[i][k]);
// for (int i = 1; i < n + 1; i++){
// for (int j = 1; j < n + 1; j++)
// cout << i << ' ' << j << ' ' << dis[i][j] << ' ' << w[i][j] << endl;
// }
ll l = 1, r = 1e9;
while (r - l > 1){
ll mid = (l + r) / 2;
//cout << "this is mid " << mid << endl;
for (int i = 1; i < n + 1; i++)
for (int j = 1; j < n + 1; j++){
sid[i][j] = -(w[i][j] - (dis[i][j] * mid));
//cout << i << ' ' << j << ' ' << sid[i][j] << endl;
}
for (int k = 1; k < n + 1; k++){
//cout << k << " :" << endl;
for (int i = 1; i < n + 1; i++){
for (int j = 1; j < n + 1; j++){
if (sid[i][j] > sid[i][k] + sid[k][j]){
//cout << i << ' ' << j << ' ' << sid[i][j] << ' ' << sid[i][k] << ' ' << sid[k][j] << ' ' << sid[i][k] + sid[k][j] << endl;
sid[i][j] = sid[i][k] + sid[k][j];
}
}
}
}
bool manf = 0;
for (int i = 1; i < n + 1; i++)
if (sid[i][i] <= 0)
manf = 1;
if (manf){
l = mid;
}
else
r = mid;
}
cout << l << endl;
}
int main(){
sariE;// filE;
int test = 1;
//cin >> test;
while (test--) Solve();
return 0;
}
