#include <bits/stdc++.h>
#define ff first
#define ss second
#define INF (1LL << 49)
using namespace std;
typedef long long int ll;
typedef pair<ll, ll> pii;
int n;
pii itens[128][1024];
ll dist[128], _dist[128];
vector<pii> adj[128], _adj[128];
void dijkstra(int x){
priority_queue<pii, vector<pii>, greater<pii>> pq;
for(int i = 0; i <= n; ++i) dist[i] = INF;
pii u;
dist[x] = 0;
pq.push(pii(0, x));
while(pq.size()){
u = pq.top(), pq.pop();
if(dist[u.ss] != u.ff) continue;
for(pii &v: adj[u.ss])
if(dist[v.ss] > v.ff + u.ff){
dist[v.ss] = v.ff + u.ff;
pq.push(pii(dist[v.ss], v.ss));
}
}
}
void _dijkstra(int x){
priority_queue<pii, vector<pii>, greater<pii>> pq;
for(int i = 0; i <= n; ++i) _dist[i] = INF;
pii u;
_dist[x] = 0;
pq.push(pii(0, x));
while(pq.size()){
u = pq.top(), pq.pop();
if(_dist[u.ss] != u.ff) continue;
for(pii &v: _adj[u.ss])
if(_dist[v.ss] > v.ff + u.ff){
_dist[v.ss] = v.ff + u.ff;
pq.push(pii(_dist[v.ss], v.ss));
}
}
}
int main(){
cin.tie(0);
ios_base::sync_with_stdio(0);
ll ans = 0;
int m, k, a, b, c;
cin >> n >> m >> k;
for(int i = 1; i <= n; ++i){
for(int j = 1; j <= k; ++j){
cin >> itens[i][j].ff >> itens[i][j].ss;
if(itens[i][j].ff == -1) itens[i][j].ff = INF;
if(itens[i][j].ss == -1) itens[i][j].ff = -INF;
}
}
for(int i = 0; i < m; ++i){
cin >> a >> b >> c;
adj[a].push_back(pii(c, b));
_adj[b].push_back(pii(c, a));
}
dijkstra(1), _dijkstra(1);
for(int i = 2; i <= n; ++i)
for(int j = 1; j <= k; ++j)
ans = max(ans, (itens[i][j].ss - itens[1][j].ff)/(dist[i] + _dist[i]));
cout << ans << "\n";
return 0;
}
