#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
int n,m,k;
vector<pll> items[101];
ll time_[101][101];
ll price[101][101];
ll dist[101][101];
bool check(ll x)
{
rep2(i,1,n) rep2(j,1,n) dist[i][j] = -1e18;
rep2(i,1,n) rep2(j,1,n) if(time_[i][j] != 1e18) dist[i][j] = max(dist[i][j],price[i][j]-x*time_[i][j]);
rep2(i2,1,n) rep2(i,1,n) rep2(j,1,n) dist[i][j] = max(dist[i][j],dist[i][i2]+dist[i2][j]);
rep2(i,1,n) rep2(j,1,n) if(i != j && dist[i][j]+dist[j][i] >= 0) return 1;
return 0;
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random_start();
cin >> n >> m >> k;
rep2(i,1,n) rep2(j,1,n) time_[i][j] = 1e18;
rep2(i,1,n) time_[i][i] = 0;
rep(i,n) rep(j,k)
{
ll a,b;
cin >> a >> b;
items[i+1].pb({a,b});
}
rep(i,m)
{
int a,b;
ll c;
cin >> a >> b >> c;
time_[a][b] = min(time_[a][b],c);
}
rep2(i2,1,n) rep2(i,1,n) rep2(j,1,n) time_[i][j] = min(time_[i][j],time_[i][i2]+time_[i2][j]);
rep2(i,1,n) rep2(j,1,n)
{
price[i][j] = 0;
rep(kk,k) if(items[j][kk].ff != -1 && items[i][kk].ss != -1) price[i][j] = max(price[i][j],items[j][kk].ss-items[i][kk].ff);
}
ll l = 0;
ll r = 1e9;
ll ans = 0;
while(l <= r)
{
ll mid = (l+r)/2;
if(check(mid))
{
ans = mid;
l = mid+1;
}
else
{
r = mid-1;
}
}
cout << ans << "\n";
}
